TOMOYO Linux Cross Reference
Linux/kernel/sched/fair.c

   // SPDX-License-Identifier: GPL-2.0
   /*
    * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
    *
    *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
    *
    *  Interactivity improvements by Mike Galbraith
    *  (C) 2007 Mike Galbraith <efault@gmx.de>
    *
   *  Various enhancements by Dmitry Adamushko.
   *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
   *
   *  Group scheduling enhancements by Srivatsa Vaddagiri
   *  Copyright IBM Corporation, 2007
   *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
   *
   *  Scaled math optimizations by Thomas Gleixner
   *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
   *
   *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
   *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
   */
  #include "sched.h"
  
  #include <trace/events/sched.h>
  
  /*
   * Targeted preemption latency for CPU-bound tasks:
   *
   * NOTE: this latency value is not the same as the concept of
   * 'timeslice length' - timeslices in CFS are of variable length
   * and have no persistent notion like in traditional, time-slice
   * based scheduling concepts.
   *
   * (to see the precise effective timeslice length of your workload,
   *  run vmstat and monitor the context-switches (cs) field)
   *
   * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
   */
  unsigned int sysctl_sched_latency                       = 6000000ULL;
  unsigned int normalized_sysctl_sched_latency            = 6000000ULL;
  
  /*
   * The initial- and re-scaling of tunables is configurable
   *
   * Options are:
   *
   *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
   *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
   *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
   *
   * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
   */
  enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
  
  /*
   * Minimal preemption granularity for CPU-bound tasks:
   *
   * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
   */
  unsigned int sysctl_sched_min_granularity               = 750000ULL;
  unsigned int normalized_sysctl_sched_min_granularity    = 750000ULL;
  
  /*
   * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
   */
  static unsigned int sched_nr_latency = 8;
  
  /*
   * After fork, child runs first. If set to 0 (default) then
   * parent will (try to) run first.
   */
  unsigned int sysctl_sched_child_runs_first __read_mostly;
  
  /*
   * SCHED_OTHER wake-up granularity.
   *
   * This option delays the preemption effects of decoupled workloads
   * and reduces their over-scheduling. Synchronous workloads will still
   * have immediate wakeup/sleep latencies.
   *
   * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
   */
  unsigned int sysctl_sched_wakeup_granularity            = 1000000UL;
  unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
  
  const_debug unsigned int sysctl_sched_migration_cost    = 500000UL;
  
  #ifdef CONFIG_SMP
  /*
   * For asym packing, by default the lower numbered CPU has higher priority.
   */
  int __weak arch_asym_cpu_priority(int cpu)
  {
          return -cpu;
  }
  #endif
  
  #ifdef CONFIG_CFS_BANDWIDTH
 /*
  * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
  * each time a cfs_rq requests quota.
  *
  * Note: in the case that the slice exceeds the runtime remaining (either due
  * to consumption or the quota being specified to be smaller than the slice)
  * we will always only issue the remaining available time.
  *
  * (default: 5 msec, units: microseconds)
  */
 unsigned int sysctl_sched_cfs_bandwidth_slice           = 5000UL;
 #endif
 
 /*
  * The margin used when comparing utilization with CPU capacity:
  * util * margin < capacity * 1024
  *
  * (default: ~20%)
  */
 unsigned int capacity_margin                            = 1280;
 
 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 {
         lw->weight += inc;
         lw->inv_weight = 0;
 }
 
 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 {
         lw->weight -= dec;
         lw->inv_weight = 0;
 }
 
 static inline void update_load_set(struct load_weight *lw, unsigned long w)
 {
         lw->weight = w;
         lw->inv_weight = 0;
 }
 
 /*
  * Increase the granularity value when there are more CPUs,
  * because with more CPUs the 'effective latency' as visible
  * to users decreases. But the relationship is not linear,
  * so pick a second-best guess by going with the log2 of the
  * number of CPUs.
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
 static unsigned int get_update_sysctl_factor(void)
 {
         unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
         unsigned int factor;
 
         switch (sysctl_sched_tunable_scaling) {
         case SCHED_TUNABLESCALING_NONE:
                 factor = 1;
                 break;
         case SCHED_TUNABLESCALING_LINEAR:
                 factor = cpus;
                 break;
         case SCHED_TUNABLESCALING_LOG:
         default:
                 factor = 1 + ilog2(cpus);
                 break;
         }
 
         return factor;
 }
 
 static void update_sysctl(void)
 {
         unsigned int factor = get_update_sysctl_factor();
 
 #define SET_SYSCTL(name) \
         (sysctl_##name = (factor) * normalized_sysctl_##name)
         SET_SYSCTL(sched_min_granularity);
         SET_SYSCTL(sched_latency);
         SET_SYSCTL(sched_wakeup_granularity);
 #undef SET_SYSCTL
 }
 
 void sched_init_granularity(void)
 {
         update_sysctl();
 }
 
 #define WMULT_CONST     (~0U)
 #define WMULT_SHIFT     32
 
 static void __update_inv_weight(struct load_weight *lw)
 {
         unsigned long w;
 
         if (likely(lw->inv_weight))
                 return;
 
         w = scale_load_down(lw->weight);
 
         if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
                 lw->inv_weight = 1;
         else if (unlikely(!w))
                 lw->inv_weight = WMULT_CONST;
         else
                 lw->inv_weight = WMULT_CONST / w;
 }
 
 /*
  * delta_exec * weight / lw.weight
  *   OR
  * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
  *
  * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
  * we're guaranteed shift stays positive because inv_weight is guaranteed to
  * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
  *
  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
  * weight/lw.weight <= 1, and therefore our shift will also be positive.
  */
 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
 {
         u64 fact = scale_load_down(weight);
         int shift = WMULT_SHIFT;
 
         __update_inv_weight(lw);
 
         if (unlikely(fact >> 32)) {
                 while (fact >> 32) {
                         fact >>= 1;
                         shift--;
                 }
         }
 
         /* hint to use a 32x32->64 mul */
         fact = (u64)(u32)fact * lw->inv_weight;
 
         while (fact >> 32) {
                 fact >>= 1;
                 shift--;
         }
 
         return mul_u64_u32_shr(delta_exec, fact, shift);
 }
 
 
 const struct sched_class fair_sched_class;
 
 /**************************************************************
  * CFS operations on generic schedulable entities:
  */
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 /* cpu runqueue to which this cfs_rq is attached */
 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 {
         return cfs_rq->rq;
 }
 
 /* An entity is a task if it doesn't "own" a runqueue */
 #define entity_is_task(se)      (!se->my_q)
 
 static inline struct task_struct *task_of(struct sched_entity *se)
 {
         SCHED_WARN_ON(!entity_is_task(se));
         return container_of(se, struct task_struct, se);
 }
 
 /* Walk up scheduling entities hierarchy */
 #define for_each_sched_entity(se) \
                 for (; se; se = se->parent)
 
 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 {
         return p->se.cfs_rq;
 }
 
 /* runqueue on which this entity is (to be) queued */
 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 {
         return se->cfs_rq;
 }
 
 /* runqueue "owned" by this group */
 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 {
         return grp->my_q;
 }
 
 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
         if (!cfs_rq->on_list) {
                 struct rq *rq = rq_of(cfs_rq);
                 int cpu = cpu_of(rq);
                 /*
                  * Ensure we either appear before our parent (if already
                  * enqueued) or force our parent to appear after us when it is
                  * enqueued. The fact that we always enqueue bottom-up
                  * reduces this to two cases and a special case for the root
                  * cfs_rq. Furthermore, it also means that we will always reset
                  * tmp_alone_branch either when the branch is connected
                  * to a tree or when we reach the beg of the tree
                  */
                 if (cfs_rq->tg->parent &&
                     cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
                         /*
                          * If parent is already on the list, we add the child
                          * just before. Thanks to circular linked property of
                          * the list, this means to put the child at the tail
                          * of the list that starts by parent.
                          */
                         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
                                 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
                         /*
                          * The branch is now connected to its tree so we can
                          * reset tmp_alone_branch to the beginning of the
                          * list.
                          */
                         rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
                 } else if (!cfs_rq->tg->parent) {
                         /*
                          * cfs rq without parent should be put
                          * at the tail of the list.
                          */
                         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
                                 &rq->leaf_cfs_rq_list);
                         /*
                          * We have reach the beg of a tree so we can reset
                          * tmp_alone_branch to the beginning of the list.
                          */
                         rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
                 } else {
                         /*
                          * The parent has not already been added so we want to
                          * make sure that it will be put after us.
                          * tmp_alone_branch points to the beg of the branch
                          * where we will add parent.
                          */
                         list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
                                 rq->tmp_alone_branch);
                         /*
                          * update tmp_alone_branch to points to the new beg
                          * of the branch
                          */
                         rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
                 }
 
                 cfs_rq->on_list = 1;
         }
 }
 
 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
         if (cfs_rq->on_list) {
                 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
                 cfs_rq->on_list = 0;
         }
 }
 
 /* Iterate thr' all leaf cfs_rq's on a runqueue */
 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)                      \
         list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list,    \
                                  leaf_cfs_rq_list)
 
 /* Do the two (enqueued) entities belong to the same group ? */
 static inline struct cfs_rq *
 is_same_group(struct sched_entity *se, struct sched_entity *pse)
 {
         if (se->cfs_rq == pse->cfs_rq)
                 return se->cfs_rq;
 
         return NULL;
 }
 
 static inline struct sched_entity *parent_entity(struct sched_entity *se)
 {
         return se->parent;
 }
 
 static void
 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 {
         int se_depth, pse_depth;
 
         /*
          * preemption test can be made between sibling entities who are in the
          * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
          * both tasks until we find their ancestors who are siblings of common
          * parent.
          */
 
         /* First walk up until both entities are at same depth */
         se_depth = (*se)->depth;
         pse_depth = (*pse)->depth;
 
         while (se_depth > pse_depth) {
                 se_depth--;
                 *se = parent_entity(*se);
         }
 
         while (pse_depth > se_depth) {
                 pse_depth--;
                 *pse = parent_entity(*pse);
         }
 
         while (!is_same_group(*se, *pse)) {
                 *se = parent_entity(*se);
                 *pse = parent_entity(*pse);
         }
 }
 
 #else   /* !CONFIG_FAIR_GROUP_SCHED */
 
 static inline struct task_struct *task_of(struct sched_entity *se)
 {
         return container_of(se, struct task_struct, se);
 }
 
 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 {
         return container_of(cfs_rq, struct rq, cfs);
 }
 
 #define entity_is_task(se)      1
 
 #define for_each_sched_entity(se) \
                 for (; se; se = NULL)
 
 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 {
         return &task_rq(p)->cfs;
 }
 
 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 {
         struct task_struct *p = task_of(se);
         struct rq *rq = task_rq(p);
 
         return &rq->cfs;
 }
 
 /* runqueue "owned" by this group */
 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 {
         return NULL;
 }
 
 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
 }
 
 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
 }
 
 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)      \
                 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
 
 static inline struct sched_entity *parent_entity(struct sched_entity *se)
 {
         return NULL;
 }
 
 static inline void
 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 {
 }
 
 #endif  /* CONFIG_FAIR_GROUP_SCHED */
 
 static __always_inline
 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
 
 /**************************************************************
  * Scheduling class tree data structure manipulation methods:
  */
 
 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 {
         s64 delta = (s64)(vruntime - max_vruntime);
         if (delta > 0)
                 max_vruntime = vruntime;
 
         return max_vruntime;
 }
 
 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 {
         s64 delta = (s64)(vruntime - min_vruntime);
         if (delta < 0)
                 min_vruntime = vruntime;
 
         return min_vruntime;
 }
 
 static inline int entity_before(struct sched_entity *a,
                                 struct sched_entity *b)
 {
         return (s64)(a->vruntime - b->vruntime) < 0;
 }
 
 static void update_min_vruntime(struct cfs_rq *cfs_rq)
 {
         struct sched_entity *curr = cfs_rq->curr;
         struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
 
         u64 vruntime = cfs_rq->min_vruntime;
 
         if (curr) {
                 if (curr->on_rq)
                         vruntime = curr->vruntime;
                 else
                         curr = NULL;
         }
 
         if (leftmost) { /* non-empty tree */
                 struct sched_entity *se;
                 se = rb_entry(leftmost, struct sched_entity, run_node);
 
                 if (!curr)
                         vruntime = se->vruntime;
                 else
                         vruntime = min_vruntime(vruntime, se->vruntime);
         }
 
         /* ensure we never gain time by being placed backwards. */
         cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
 #ifndef CONFIG_64BIT
         smp_wmb();
         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
 #endif
 }
 
 /*
  * Enqueue an entity into the rb-tree:
  */
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
         struct rb_node *parent = NULL;
         struct sched_entity *entry;
         bool leftmost = true;
 
         /*
          * Find the right place in the rbtree:
          */
         while (*link) {
                 parent = *link;
                 entry = rb_entry(parent, struct sched_entity, run_node);
                 /*
                  * We dont care about collisions. Nodes with
                  * the same key stay together.
                  */
                 if (entity_before(se, entry)) {
                         link = &parent->rb_left;
                 } else {
                         link = &parent->rb_right;
                         leftmost = false;
                 }
         }
 
         rb_link_node(&se->run_node, parent, link);
         rb_insert_color_cached(&se->run_node,
                                &cfs_rq->tasks_timeline, leftmost);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
 }
 
 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 {
         struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
 
         if (!left)
                 return NULL;
 
         return rb_entry(left, struct sched_entity, run_node);
 }
 
 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
 {
         struct rb_node *next = rb_next(&se->run_node);
 
         if (!next)
                 return NULL;
 
         return rb_entry(next, struct sched_entity, run_node);
 }
 
 #ifdef CONFIG_SCHED_DEBUG
 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
         struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
 
         if (!last)
                 return NULL;
 
         return rb_entry(last, struct sched_entity, run_node);
 }
 
 /**************************************************************
  * Scheduling class statistics methods:
  */
 
 int sched_proc_update_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos)
 {
         int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
         unsigned int factor = get_update_sysctl_factor();
 
         if (ret || !write)
                 return ret;
 
         sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
                                         sysctl_sched_min_granularity);
 
 #define WRT_SYSCTL(name) \
         (normalized_sysctl_##name = sysctl_##name / (factor))
         WRT_SYSCTL(sched_min_granularity);
         WRT_SYSCTL(sched_latency);
         WRT_SYSCTL(sched_wakeup_granularity);
 #undef WRT_SYSCTL
 
         return 0;
 }
 #endif
 
 /*
  * delta /= w
  */
 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
 {
         if (unlikely(se->load.weight != NICE_0_LOAD))
                 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
 
         return delta;
 }
 
 /*
  * The idea is to set a period in which each task runs once.
  *
  * When there are too many tasks (sched_nr_latency) we have to stretch
  * this period because otherwise the slices get too small.
  *
  * p = (nr <= nl) ? l : l*nr/nl
  */
 static u64 __sched_period(unsigned long nr_running)
 {
         if (unlikely(nr_running > sched_nr_latency))
                 return nr_running * sysctl_sched_min_granularity;
         else
                 return sysctl_sched_latency;
 }
 
 /*
  * We calculate the wall-time slice from the period by taking a part
  * proportional to the weight.
  *
  * s = p*P[w/rw]
  */
 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
 
         for_each_sched_entity(se) {
                 struct load_weight *load;
                 struct load_weight lw;
 
                 cfs_rq = cfs_rq_of(se);
                 load = &cfs_rq->load;
 
                 if (unlikely(!se->on_rq)) {
                         lw = cfs_rq->load;
 
                         update_load_add(&lw, se->load.weight);
                         load = &lw;
                 }
                 slice = __calc_delta(slice, se->load.weight, load);
         }
         return slice;
 }
 
 /*
  * We calculate the vruntime slice of a to-be-inserted task.
  *
  * vs = s/w
  */
 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         return calc_delta_fair(sched_slice(cfs_rq, se), se);
 }
 
 #ifdef CONFIG_SMP
 
 #include "sched-pelt.h"
 
 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
 static unsigned long task_h_load(struct task_struct *p);
 
 /* Give new sched_entity start runnable values to heavy its load in infant time */
 void init_entity_runnable_average(struct sched_entity *se)
 {
         struct sched_avg *sa = &se->avg;
 
         memset(sa, 0, sizeof(*sa));
 
         /*
          * Tasks are intialized with full load to be seen as heavy tasks until
          * they get a chance to stabilize to their real load level.
          * Group entities are intialized with zero load to reflect the fact that
          * nothing has been attached to the task group yet.
          */
         if (entity_is_task(se))
                 sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);
 
         se->runnable_weight = se->load.weight;
 
         /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
 }
 
 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
 static void attach_entity_cfs_rq(struct sched_entity *se);
 
 /*
  * With new tasks being created, their initial util_avgs are extrapolated
  * based on the cfs_rq's current util_avg:
  *
  *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
  *
  * However, in many cases, the above util_avg does not give a desired
  * value. Moreover, the sum of the util_avgs may be divergent, such
  * as when the series is a harmonic series.
  *
  * To solve this problem, we also cap the util_avg of successive tasks to
  * only 1/2 of the left utilization budget:
  *
  *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
  *
  * where n denotes the nth task.
  *
  * For example, a simplest series from the beginning would be like:
  *
  *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
  * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
  *
  * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
  * if util_avg > util_avg_cap.
  */
 void post_init_entity_util_avg(struct sched_entity *se)
 {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         struct sched_avg *sa = &se->avg;
         long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
 
         if (cap > 0) {
                 if (cfs_rq->avg.util_avg != 0) {
                         sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
                         sa->util_avg /= (cfs_rq->avg.load_avg + 1);
 
                         if (sa->util_avg > cap)
                                 sa->util_avg = cap;
                 } else {
                         sa->util_avg = cap;
                 }
         }
 
         if (entity_is_task(se)) {
                 struct task_struct *p = task_of(se);
                 if (p->sched_class != &fair_sched_class) {
                         /*
                          * For !fair tasks do:
                          *
                         update_cfs_rq_load_avg(now, cfs_rq);
                         attach_entity_load_avg(cfs_rq, se, 0);
                         switched_from_fair(rq, p);
                          *
                          * such that the next switched_to_fair() has the
                          * expected state.
                          */
                         se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
                         return;
                 }
         }
 
         attach_entity_cfs_rq(se);
 }
 
 #else /* !CONFIG_SMP */
 void init_entity_runnable_average(struct sched_entity *se)
 {
 }
 void post_init_entity_util_avg(struct sched_entity *se)
 {
 }
 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
 {
 }
 #endif /* CONFIG_SMP */
 
 /*
  * Update the current task's runtime statistics.
  */
 static void update_curr(struct cfs_rq *cfs_rq)
 {
         struct sched_entity *curr = cfs_rq->curr;
         u64 now = rq_clock_task(rq_of(cfs_rq));
         u64 delta_exec;
 
         if (unlikely(!curr))
                 return;
 
         delta_exec = now - curr->exec_start;
         if (unlikely((s64)delta_exec <= 0))
                 return;
 
         curr->exec_start = now;
 
         schedstat_set(curr->statistics.exec_max,
                       max(delta_exec, curr->statistics.exec_max));
 
         curr->sum_exec_runtime += delta_exec;
         schedstat_add(cfs_rq->exec_clock, delta_exec);
 
         curr->vruntime += calc_delta_fair(delta_exec, curr);
         update_min_vruntime(cfs_rq);
 
         if (entity_is_task(curr)) {
                 struct task_struct *curtask = task_of(curr);
 
                 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
                 cgroup_account_cputime(curtask, delta_exec);
                 account_group_exec_runtime(curtask, delta_exec);
         }
 
         account_cfs_rq_runtime(cfs_rq, delta_exec);
 }
 
 static void update_curr_fair(struct rq *rq)
 {
         update_curr(cfs_rq_of(&rq->curr->se));
 }
 
 static inline void
 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         u64 wait_start, prev_wait_start;
 
         if (!schedstat_enabled())
                 return;
 
         wait_start = rq_clock(rq_of(cfs_rq));
         prev_wait_start = schedstat_val(se->statistics.wait_start);
 
         if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
             likely(wait_start > prev_wait_start))
                 wait_start -= prev_wait_start;
 
         __schedstat_set(se->statistics.wait_start, wait_start);
 }
 
 static inline void
 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         struct task_struct *p;
         u64 delta;
 
         if (!schedstat_enabled())
                 return;
 
         delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
 
         if (entity_is_task(se)) {
                 p = task_of(se);
                 if (task_on_rq_migrating(p)) {
                         /*
                          * Preserve migrating task's wait time so wait_start
                          * time stamp can be adjusted to accumulate wait time
                          * prior to migration.
                          */
                         __schedstat_set(se->statistics.wait_start, delta);
                         return;
                 }
                 trace_sched_stat_wait(p, delta);
         }
 
         __schedstat_set(se->statistics.wait_max,
                       max(schedstat_val(se->statistics.wait_max), delta));
         __schedstat_inc(se->statistics.wait_count);
         __schedstat_add(se->statistics.wait_sum, delta);
         __schedstat_set(se->statistics.wait_start, 0);
 }
 
 static inline void
 update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         struct task_struct *tsk = NULL;
         u64 sleep_start, block_start;
 
         if (!schedstat_enabled())
                 return;
 
         sleep_start = schedstat_val(se->statistics.sleep_start);
         block_start = schedstat_val(se->statistics.block_start);
 
         if (entity_is_task(se))
                 tsk = task_of(se);
 
         if (sleep_start) {
                 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
 
                 if ((s64)delta < 0)
                         delta = 0;
 
                 if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
                         __schedstat_set(se->statistics.sleep_max, delta);
 
                 __schedstat_set(se->statistics.sleep_start, 0);
                 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
 
                 if (tsk) {
                         account_scheduler_latency(tsk, delta >> 10, 1);
                         trace_sched_stat_sleep(tsk, delta);
                 }
         }
         if (block_start) {
                 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
 
                 if ((s64)delta < 0)
                         delta = 0;
 
                 if (unlikely(delta > schedstat_val(se->statistics.block_max)))
                         __schedstat_set(se->statistics.block_max, delta);
 
                 __schedstat_set(se->statistics.block_start, 0);
                 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
 
                 if (tsk) {
                         if (tsk->in_iowait) {
                                 __schedstat_add(se->statistics.iowait_sum, delta);
                                 __schedstat_inc(se->statistics.iowait_count);
                                 trace_sched_stat_iowait(tsk, delta);
                         }
 
                         trace_sched_stat_blocked(tsk, delta);
 
                         /*
                          * Blocking time is in units of nanosecs, so shift by
                          * 20 to get a milliseconds-range estimation of the
                          * amount of time that the task spent sleeping:
                          */
                         if (unlikely(prof_on == SLEEP_PROFILING)) {
                                 profile_hits(SLEEP_PROFILING,
                                                 (void *)get_wchan(tsk),
                                                 delta >> 20);
                         }
                         account_scheduler_latency(tsk, delta >> 10, 0);
                 }
         }
 }
 
 /*
  * Task is being enqueued - update stats:
  */
 static inline void
 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
         if (!schedstat_enabled())
                 return;
 
         /*
          * Are we enqueueing a waiting task? (for current tasks
          * a dequeue/enqueue event is a NOP)
          */
         if (se != cfs_rq->curr)
                 update_stats_wait_start(cfs_rq, se);
 
         if (flags & ENQUEUE_WAKEUP)
                 update_stats_enqueue_sleeper(cfs_rq, se);
 }
 
 static inline void
 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
 
         if (!schedstat_enabled())
                 return;
 
         /*
          * Mark the end of the wait period if dequeueing a
          * waiting task:
          */
         if (se != cfs_rq->curr)
                 update_stats_wait_end(cfs_rq, se);
 
         if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
                 struct task_struct *tsk = task_of(se);
 
                 if (tsk->state & TASK_INTERRUPTIBLE)
                         __schedstat_set(se->statistics.sleep_start,
                                       rq_clock(rq_of(cfs_rq)));
                 if (tsk->state & TASK_UNINTERRUPTIBLE)
                         __schedstat_set(se->statistics.block_start,
                                       rq_clock(rq_of(cfs_rq)));
         }
 }
 
 /*
  * We are picking a new current task - update its stats:
  */
 static inline void
 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         /*
          * We are starting a new run period:
          */
         se->exec_start = rq_clock_task(rq_of(cfs_rq));
 }
 
 /**************************************************
  * Scheduling class queueing methods:
  */
 
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * Approximate time to scan a full NUMA task in ms. The task scan period is
  * calculated based on the tasks virtual memory size and
  * numa_balancing_scan_size.
  */
 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
 
 /* Portion of address space to scan in MB */
 unsigned int sysctl_numa_balancing_scan_size = 256;
 
 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
 unsigned int sysctl_numa_balancing_scan_delay = 1000;
 
 struct numa_group {
         atomic_t refcount;
 
         spinlock_t lock; /* nr_tasks, tasks */
         int nr_tasks;
         pid_t gid;
         int active_nodes;
 
         struct rcu_head rcu;
         unsigned long total_faults;
         unsigned long max_faults_cpu;
         /*
          * Faults_cpu is used to decide whether memory should move
          * towards the CPU. As a consequence, these stats are weighted
          * more by CPU use than by memory faults.
          */
         unsigned long *faults_cpu;
         unsigned long faults[0];
 };
 
 static inline unsigned long group_faults_priv(struct numa_group *ng);
 static inline unsigned long group_faults_shared(struct numa_group *ng);
 
 static unsigned int task_nr_scan_windows(struct task_struct *p)
 {
         unsigned long rss = 0;
         unsigned long nr_scan_pages;
 
         /*
          * Calculations based on RSS as non-present and empty pages are skipped
          * by the PTE scanner and NUMA hinting faults should be trapped based
          * on resident pages
          */
         nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
         rss = get_mm_rss(p->mm);
         if (!rss)
                 rss = nr_scan_pages;
 
         rss = round_up(rss, nr_scan_pages);
         return rss / nr_scan_pages;
 }
 
 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
 #define MAX_SCAN_WINDOW 2560
 
 static unsigned int task_scan_min(struct task_struct *p)
 {
         unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
         unsigned int scan, floor;
         unsigned int windows = 1;
 
         if (scan_size < MAX_SCAN_WINDOW)
                 windows = MAX_SCAN_WINDOW / scan_size;
         floor = 1000 / windows;
 
         scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
         return max_t(unsigned int, floor, scan);
 }
 
 static unsigned int task_scan_start(struct task_struct *p)
 {
         unsigned long smin = task_scan_min(p);
         unsigned long period = smin;
 
         /* Scale the maximum scan period with the amount of shared memory. */
         if (p->numa_group) {
                 struct numa_group *ng = p->numa_group;
                 unsigned long shared = group_faults_shared(ng);
                 unsigned long private = group_faults_priv(ng);
 
                 period *= atomic_read(&ng->refcount);
                 period *= shared + 1;
                 period /= private + shared + 1;
         }
 
         return max(smin, period);
 }
 
 static unsigned int task_scan_max(struct task_struct *p)
 {
         unsigned long smin = task_scan_min(p);
         unsigned long smax;
 
         /* Watch for min being lower than max due to floor calculations */
         smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
 
         /* Scale the maximum scan period with the amount of shared memory. */
         if (p->numa_group) {
                 struct numa_group *ng = p->numa_group;
                 unsigned long shared = group_faults_shared(ng);
                 unsigned long private = group_faults_priv(ng);
                 unsigned long period = smax;
 
                 period *= atomic_read(&ng->refcount);
                 period *= shared + 1;
                 period /= private + shared + 1;
 
                 smax = max(smax, period);
         }
 
         return max(smin, smax);
 }
 
 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
 {
         rq->nr_numa_running += (p->numa_preferred_nid != -1);
         rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
 }
 
 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
 {
         rq->nr_numa_running -= (p->numa_preferred_nid != -1);
         rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
 }
 
 /* Shared or private faults. */
 #define NR_NUMA_HINT_FAULT_TYPES 2
 
 /* Memory and CPU locality */
 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
 
 /* Averaged statistics, and temporary buffers. */
 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
 
 pid_t task_numa_group_id(struct task_struct *p)
 {
         return p->numa_group ? p->numa_group->gid : 0;
 }
 
 /*
  * The averaged statistics, shared & private, memory & CPU,
  * occupy the first half of the array. The second half of the
  * array is for current counters, which are averaged into the
  * first set by task_numa_placement.
  */
 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
 {
         return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
 }
 
 static inline unsigned long task_faults(struct task_struct *p, int nid)
 {
         if (!p->numa_faults)
                 return 0;
 
         return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
                 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
 }
 
 static inline unsigned long group_faults(struct task_struct *p, int nid)
 {
         if (!p->numa_group)
                 return 0;
 
         return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
                 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
 }
 
 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
 {
         return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
                 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
 }
 
 static inline unsigned long group_faults_priv(struct numa_group *ng)
 {
         unsigned long faults = 0;
         int node;
 
         for_each_online_node(node) {
                 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
         }
 
         return faults;
 }
 
 static inline unsigned long group_faults_shared(struct numa_group *ng)
 {
         unsigned long faults = 0;
         int node;
 
         for_each_online_node(node) {
                 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
         }
 
         return faults;
 }
 
 /*
  * A node triggering more than 1/3 as many NUMA faults as the maximum is
  * considered part of a numa group's pseudo-interleaving set. Migrations
  * between these nodes are slowed down, to allow things to settle down.
  */
 #define ACTIVE_NODE_FRACTION 3
 
 static bool numa_is_active_node(int nid, struct numa_group *ng)
 {
         return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
 }
 
 /* Handle placement on systems where not all nodes are directly connected. */
 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
                                         int maxdist, bool task)
 {
         unsigned long score = 0;
         int node;
 
         /*
          * All nodes are directly connected, and the same distance
          * from each other. No need for fancy placement algorithms.
          */
         if (sched_numa_topology_type == NUMA_DIRECT)
                 return 0;
 
         /*
          * This code is called for each node, introducing N^2 complexity,
          * which should be ok given the number of nodes rarely exceeds 8.
          */
         for_each_online_node(node) {
                 unsigned long faults;
                 int dist = node_distance(nid, node);
 
                 /*
                  * The furthest away nodes in the system are not interesting
                  * for placement; nid was already counted.
                  */
                 if (dist == sched_max_numa_distance || node == nid)
                         continue;
 
                 /*
                  * On systems with a backplane NUMA topology, compare groups
                  * of nodes, and move tasks towards the group with the most
                  * memory accesses. When comparing two nodes at distance
                  * "hoplimit", only nodes closer by than "hoplimit" are part
                  * of each group. Skip other nodes.
                  */
                 if (sched_numa_topology_type == NUMA_BACKPLANE &&
                                         dist > maxdist)
                         continue;
 
                 /* Add up the faults from nearby nodes. */
                 if (task)
                         faults = task_faults(p, node);
                 else
                         faults = group_faults(p, node);
 
                 /*
                  * On systems with a glueless mesh NUMA topology, there are
                  * no fixed "groups of nodes". Instead, nodes that are not
                  * directly connected bounce traffic through intermediate
                  * nodes; a numa_group can occupy any set of nodes.
                  * The further away a node is, the less the faults count.
                  * This seems to result in good task placement.
                  */
                 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
                         faults *= (sched_max_numa_distance - dist);
                         faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
                 }
 
                 score += faults;
         }
 
         return score;
 }
 
 /*
  * These return the fraction of accesses done by a particular task, or
  * task group, on a particular numa node.  The group weight is given a
  * larger multiplier, in order to group tasks together that are almost
  * evenly spread out between numa nodes.
  */
 static inline unsigned long task_weight(struct task_struct *p, int nid,
                                         int dist)
 {
         unsigned long faults, total_faults;
 
         if (!p->numa_faults)
                 return 0;
 
         total_faults = p->total_numa_faults;
 
         if (!total_faults)
                 return 0;
 
         faults = task_faults(p, nid);
         faults += score_nearby_nodes(p, nid, dist, true);
 
         return 1000 * faults / total_faults;
 }
 
 static inline unsigned long group_weight(struct task_struct *p, int nid,
                                          int dist)
 {
         unsigned long faults, total_faults;
 
         if (!p->numa_group)
                 return 0;
 
         total_faults = p->numa_group->total_faults;
 
         if (!total_faults)
                 return 0;
 
         faults = group_faults(p, nid);
         faults += score_nearby_nodes(p, nid, dist, false);
 
         return 1000 * faults / total_faults;
 }
 
 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
                                 int src_nid, int dst_cpu)
 {
         struct numa_group *ng = p->numa_group;
         int dst_nid = cpu_to_node(dst_cpu);
         int last_cpupid, this_cpupid;
 
         this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
 
         /*
          * Multi-stage node selection is used in conjunction with a periodic
          * migration fault to build a temporal task<->page relation. By using
          * a two-stage filter we remove short/unlikely relations.
          *
          * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
          * a task's usage of a particular page (n_p) per total usage of this
          * page (n_t) (in a given time-span) to a probability.
          *
          * Our periodic faults will sample this probability and getting the
          * same result twice in a row, given these samples are fully
          * independent, is then given by P(n)^2, provided our sample period
          * is sufficiently short compared to the usage pattern.
          *
          * This quadric squishes small probabilities, making it less likely we
          * act on an unlikely task<->page relation.
          */
         last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
         if (!cpupid_pid_unset(last_cpupid) &&
                                 cpupid_to_nid(last_cpupid) != dst_nid)
                 return false;
 
         /* Always allow migrate on private faults */
         if (cpupid_match_pid(p, last_cpupid))
                 return true;
 
         /* A shared fault, but p->numa_group has not been set up yet. */
         if (!ng)
                 return true;
 
         /*
          * Destination node is much more heavily used than the source
          * node? Allow migration.
          */
         if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
                                         ACTIVE_NODE_FRACTION)
                 return true;
 
         /*
          * Distribute memory according to CPU & memory use on each node,
          * with 3/4 hysteresis to avoid unnecessary memory migrations:
          *
          * faults_cpu(dst)   3   faults_cpu(src)
          * --------------- * - > ---------------
          * faults_mem(dst)   4   faults_mem(src)
          */
         return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
                group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
 }
 
 static unsigned long weighted_cpuload(struct rq *rq);
 static unsigned long source_load(int cpu, int type);
 static unsigned long target_load(int cpu, int type);
 static unsigned long capacity_of(int cpu);
 
 /* Cached statistics for all CPUs within a node */
 struct numa_stats {
         unsigned long nr_running;
         unsigned long load;
 
         /* Total compute capacity of CPUs on a node */
         unsigned long compute_capacity;
 
         /* Approximate capacity in terms of runnable tasks on a node */
         unsigned long task_capacity;
         int has_free_capacity;
 };
 
 /*
  * XXX borrowed from update_sg_lb_stats
  */
 static void update_numa_stats(struct numa_stats *ns, int nid)
 {
         int smt, cpu, cpus = 0;
         unsigned long capacity;
 
         memset(ns, 0, sizeof(*ns));
         for_each_cpu(cpu, cpumask_of_node(nid)) {
                 struct rq *rq = cpu_rq(cpu);
 
                 ns->nr_running += rq->nr_running;
                 ns->load += weighted_cpuload(rq);
                 ns->compute_capacity += capacity_of(cpu);
 
                 cpus++;
         }
 
         /*
          * If we raced with hotplug and there are no CPUs left in our mask
          * the @ns structure is NULL'ed and task_numa_compare() will
          * not find this node attractive.
          *
          * We'll either bail at !has_free_capacity, or we'll detect a huge
          * imbalance and bail there.
          */
         if (!cpus)
                 return;
 
         /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
         smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
         capacity = cpus / smt; /* cores */
 
         ns->task_capacity = min_t(unsigned, capacity,
                 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
         ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
 }
 
 struct task_numa_env {
         struct task_struct *p;
 
         int src_cpu, src_nid;
         int dst_cpu, dst_nid;
 
         struct numa_stats src_stats, dst_stats;
 
         int imbalance_pct;
         int dist;
 
         struct task_struct *best_task;
         long best_imp;
         int best_cpu;
 };
 
 static void task_numa_assign(struct task_numa_env *env,
                              struct task_struct *p, long imp)
 {
         if (env->best_task)
                 put_task_struct(env->best_task);
         if (p)
                 get_task_struct(p);
 
         env->best_task = p;
         env->best_imp = imp;
         env->best_cpu = env->dst_cpu;
 }
 
 static bool load_too_imbalanced(long src_load, long dst_load,
                                 struct task_numa_env *env)
 {
         long imb, old_imb;
         long orig_src_load, orig_dst_load;
         long src_capacity, dst_capacity;
 
         /*
          * The load is corrected for the CPU capacity available on each node.
          *
          * src_load        dst_load
          * ------------ vs ---------
          * src_capacity    dst_capacity
          */
         src_capacity = env->src_stats.compute_capacity;
         dst_capacity = env->dst_stats.compute_capacity;
 
         /* We care about the slope of the imbalance, not the direction. */
         if (dst_load < src_load)
                 swap(dst_load, src_load);
 
         /* Is the difference below the threshold? */
         imb = dst_load * src_capacity * 100 -
               src_load * dst_capacity * env->imbalance_pct;
         if (imb <= 0)
                 return false;
 
         /*
          * The imbalance is above the allowed threshold.
          * Compare it with the old imbalance.
          */
         orig_src_load = env->src_stats.load;
         orig_dst_load = env->dst_stats.load;
 
         if (orig_dst_load < orig_src_load)
                 swap(orig_dst_load, orig_src_load);
 
         old_imb = orig_dst_load * src_capacity * 100 -
                   orig_src_load * dst_capacity * env->imbalance_pct;
 
         /* Would this change make things worse? */
         return (imb > old_imb);
 }
 
 /*
  * This checks if the overall compute and NUMA accesses of the system would
  * be improved if the source tasks was migrated to the target dst_cpu taking
  * into account that it might be best if task running on the dst_cpu should
  * be exchanged with the source task
  */
 static void task_numa_compare(struct task_numa_env *env,
                               long taskimp, long groupimp)
 {
         struct rq *src_rq = cpu_rq(env->src_cpu);
         struct rq *dst_rq = cpu_rq(env->dst_cpu);
         struct task_struct *cur;
         long src_load, dst_load;
         long load;
         long imp = env->p->numa_group ? groupimp : taskimp;
         long moveimp = imp;
         int dist = env->dist;
 
         rcu_read_lock();
         cur = task_rcu_dereference(&dst_rq->curr);
         if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
                 cur = NULL;
 
         /*
          * Because we have preemption enabled we can get migrated around and
          * end try selecting ourselves (current == env->p) as a swap candidate.
          */
         if (cur == env->p)
                 goto unlock;
 
         /*
          * "imp" is the fault differential for the source task between the
          * source and destination node. Calculate the total differential for
          * the source task and potential destination task. The more negative
          * the value is, the more rmeote accesses that would be expected to
          * be incurred if the tasks were swapped.
          */
         if (cur) {
                 /* Skip this swap candidate if cannot move to the source CPU: */
                 if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
                         goto unlock;
 
                 /*
                  * If dst and source tasks are in the same NUMA group, or not
                  * in any group then look only at task weights.
                  */
                 if (cur->numa_group == env->p->numa_group) {
                         imp = taskimp + task_weight(cur, env->src_nid, dist) -
                               task_weight(cur, env->dst_nid, dist);
                         /*
                          * Add some hysteresis to prevent swapping the
                          * tasks within a group over tiny differences.
                          */
                         if (cur->numa_group)
                                 imp -= imp/16;
                 } else {
                         /*
                          * Compare the group weights. If a task is all by
                          * itself (not part of a group), use the task weight
                          * instead.
                          */
                         if (cur->numa_group)
                                 imp += group_weight(cur, env->src_nid, dist) -
                                        group_weight(cur, env->dst_nid, dist);
                         else
                                 imp += task_weight(cur, env->src_nid, dist) -
                                        task_weight(cur, env->dst_nid, dist);
                 }
         }
 
         if (imp <= env->best_imp && moveimp <= env->best_imp)
                 goto unlock;
 
         if (!cur) {
                 /* Is there capacity at our destination? */
                 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
                     !env->dst_stats.has_free_capacity)
                         goto unlock;
 
                 goto balance;
         }
 
         /* Balance doesn't matter much if we're running a task per CPU: */
         if (imp > env->best_imp && src_rq->nr_running == 1 &&
                         dst_rq->nr_running == 1)
                 goto assign;
 
         /*
          * In the overloaded case, try and keep the load balanced.
          */
 balance:
         load = task_h_load(env->p);
         dst_load = env->dst_stats.load + load;
         src_load = env->src_stats.load - load;
 
         if (moveimp > imp && moveimp > env->best_imp) {
                 /*
                  * If the improvement from just moving env->p direction is
                  * better than swapping tasks around, check if a move is
                  * possible. Store a slightly smaller score than moveimp,
                  * so an actually idle CPU will win.
                  */
                 if (!load_too_imbalanced(src_load, dst_load, env)) {
                         imp = moveimp - 1;
                         cur = NULL;
                         goto assign;
                 }
         }
 
         if (imp <= env->best_imp)
                 goto unlock;
 
         if (cur) {
                 load = task_h_load(cur);
                 dst_load -= load;
                 src_load += load;
         }
 
         if (load_too_imbalanced(src_load, dst_load, env))
                 goto unlock;
 
         /*
          * One idle CPU per node is evaluated for a task numa move.
          * Call select_idle_sibling to maybe find a better one.
          */
         if (!cur) {
                 /*
                  * select_idle_siblings() uses an per-CPU cpumask that
                  * can be used from IRQ context.
                  */
                 local_irq_disable();
                 env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
                                                    env->dst_cpu);
                 local_irq_enable();
         }
 
 assign:
         task_numa_assign(env, cur, imp);
 unlock:
         rcu_read_unlock();
 }
 
 static void task_numa_find_cpu(struct task_numa_env *env,
                                 long taskimp, long groupimp)
 {
         int cpu;
 
         for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
                 /* Skip this CPU if the source task cannot migrate */
                 if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
                         continue;
 
                 env->dst_cpu = cpu;
                 task_numa_compare(env, taskimp, groupimp);
         }
 }
 
 /* Only move tasks to a NUMA node less busy than the current node. */
 static bool numa_has_capacity(struct task_numa_env *env)
 {
         struct numa_stats *src = &env->src_stats;
         struct numa_stats *dst = &env->dst_stats;
 
         if (src->has_free_capacity && !dst->has_free_capacity)
                 return false;
 
         /*
          * Only consider a task move if the source has a higher load
          * than the destination, corrected for CPU capacity on each node.
          *
          *      src->load                dst->load
          * --------------------- vs ---------------------
          * src->compute_capacity    dst->compute_capacity
          */
         if (src->load * dst->compute_capacity * env->imbalance_pct >
 
             dst->load * src->compute_capacity * 100)
                 return true;
 
         return false;
 }
 
 static int task_numa_migrate(struct task_struct *p)
 {
         struct task_numa_env env = {
                 .p = p,
 
                 .src_cpu = task_cpu(p),
                 .src_nid = task_node(p),
 
                 .imbalance_pct = 112,
 
                 .best_task = NULL,
                 .best_imp = 0,
                 .best_cpu = -1,
         };
         struct sched_domain *sd;
         unsigned long taskweight, groupweight;
         int nid, ret, dist;
         long taskimp, groupimp;
 
         /*
          * Pick the lowest SD_NUMA domain, as that would have the smallest
          * imbalance and would be the first to start moving tasks about.
          *
          * And we want to avoid any moving of tasks about, as that would create
          * random movement of tasks -- counter the numa conditions we're trying
          * to satisfy here.
          */
         rcu_read_lock();
         sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
         if (sd)
                 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
         rcu_read_unlock();
 
         /*
          * Cpusets can break the scheduler domain tree into smaller
          * balance domains, some of which do not cross NUMA boundaries.
          * Tasks that are "trapped" in such domains cannot be migrated
          * elsewhere, so there is no point in (re)trying.
          */
         if (unlikely(!sd)) {
                 p->numa_preferred_nid = task_node(p);
                 return -EINVAL;
         }
 
         env.dst_nid = p->numa_preferred_nid;
         dist = env.dist = node_distance(env.src_nid, env.dst_nid);
         taskweight = task_weight(p, env.src_nid, dist);
         groupweight = group_weight(p, env.src_nid, dist);
         update_numa_stats(&env.src_stats, env.src_nid);
         taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
         groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
         update_numa_stats(&env.dst_stats, env.dst_nid);
 
         /* Try to find a spot on the preferred nid. */
         if (numa_has_capacity(&env))
                 task_numa_find_cpu(&env, taskimp, groupimp);
 
         /*
          * Look at other nodes in these cases:
          * - there is no space available on the preferred_nid
          * - the task is part of a numa_group that is interleaved across
          *   multiple NUMA nodes; in order to better consolidate the group,
          *   we need to check other locations.
          */
         if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
                 for_each_online_node(nid) {
                         if (nid == env.src_nid || nid == p->numa_preferred_nid)
                                 continue;
 
                         dist = node_distance(env.src_nid, env.dst_nid);
                         if (sched_numa_topology_type == NUMA_BACKPLANE &&
                                                 dist != env.dist) {
                                 taskweight = task_weight(p, env.src_nid, dist);
                                 groupweight = group_weight(p, env.src_nid, dist);
                         }
 
                         /* Only consider nodes where both task and groups benefit */
                         taskimp = task_weight(p, nid, dist) - taskweight;
                         groupimp = group_weight(p, nid, dist) - groupweight;
                         if (taskimp < 0 && groupimp < 0)
                                 continue;
 
                         env.dist = dist;
                         env.dst_nid = nid;
                         update_numa_stats(&env.dst_stats, env.dst_nid);
                         if (numa_has_capacity(&env))
                                 task_numa_find_cpu(&env, taskimp, groupimp);
                 }
         }
 
         /*
          * If the task is part of a workload that spans multiple NUMA nodes,
          * and is migrating into one of the workload's active nodes, remember
          * this node as the task's preferred numa node, so the workload can
          * settle down.
          * A task that migrated to a second choice node will be better off
          * trying for a better one later. Do not set the preferred node here.
          */
         if (p->numa_group) {
                 struct numa_group *ng = p->numa_group;
 
                 if (env.best_cpu == -1)
                         nid = env.src_nid;
                 else
                         nid = env.dst_nid;
 
                 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
                         sched_setnuma(p, env.dst_nid);
         }
 
         /* No better CPU than the current one was found. */
         if (env.best_cpu == -1)
                 return -EAGAIN;
 
         /*
          * Reset the scan period if the task is being rescheduled on an
          * alternative node to recheck if the tasks is now properly placed.
          */
         p->numa_scan_period = task_scan_start(p);
 
         if (env.best_task == NULL) {
                 ret = migrate_task_to(p, env.best_cpu);
                 if (ret != 0)
                         trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
                 return ret;
         }
 
         ret = migrate_swap(p, env.best_task);
         if (ret != 0)
                 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
         put_task_struct(env.best_task);
         return ret;
 }
 
 /* Attempt to migrate a task to a CPU on the preferred node. */
 static void numa_migrate_preferred(struct task_struct *p)
 {
         unsigned long interval = HZ;
 
         /* This task has no NUMA fault statistics yet */
         if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
                 return;
 
         /* Periodically retry migrating the task to the preferred node */
         interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
         p->numa_migrate_retry = jiffies + interval;
 
         /* Success if task is already running on preferred CPU */
         if (task_node(p) == p->numa_preferred_nid)
                 return;
 
         /* Otherwise, try migrate to a CPU on the preferred node */
         task_numa_migrate(p);
 }
 
 /*
  * Find out how many nodes on the workload is actively running on. Do this by
  * tracking the nodes from which NUMA hinting faults are triggered. This can
  * be different from the set of nodes where the workload's memory is currently
  * located.
  */
 static void numa_group_count_active_nodes(struct numa_group *numa_group)
 {
         unsigned long faults, max_faults = 0;
         int nid, active_nodes = 0;
 
         for_each_online_node(nid) {
                 faults = group_faults_cpu(numa_group, nid);
                 if (faults > max_faults)
                         max_faults = faults;
         }
 
         for_each_online_node(nid) {
                 faults = group_faults_cpu(numa_group, nid);
                 if (faults * ACTIVE_NODE_FRACTION > max_faults)
                         active_nodes++;
         }
 
         numa_group->max_faults_cpu = max_faults;
         numa_group->active_nodes = active_nodes;
 }
 
 /*
  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
  * increments. The more local the fault statistics are, the higher the scan
  * period will be for the next scan window. If local/(local+remote) ratio is
  * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
  * the scan period will decrease. Aim for 70% local accesses.
  */
 #define NUMA_PERIOD_SLOTS 10
 #define NUMA_PERIOD_THRESHOLD 7
 
 /*
  * Increase the scan period (slow down scanning) if the majority of
  * our memory is already on our local node, or if the majority of
  * the page accesses are shared with other processes.
  * Otherwise, decrease the scan period.
  */
 static void update_task_scan_period(struct task_struct *p,
                         unsigned long shared, unsigned long private)
 {
         unsigned int period_slot;
         int lr_ratio, ps_ratio;
         int diff;
 
         unsigned long remote = p->numa_faults_locality[0];
         unsigned long local = p->numa_faults_locality[1];
 
         /*
          * If there were no record hinting faults then either the task is
          * completely idle or all activity is areas that are not of interest
          * to automatic numa balancing. Related to that, if there were failed
          * migration then it implies we are migrating too quickly or the local
          * node is overloaded. In either case, scan slower
          */
         if (local + shared == 0 || p->numa_faults_locality[2]) {
                 p->numa_scan_period = min(p->numa_scan_period_max,
                         p->numa_scan_period << 1);
 
                 p->mm->numa_next_scan = jiffies +
                         msecs_to_jiffies(p->numa_scan_period);
 
                 return;
         }
 
         /*
          * Prepare to scale scan period relative to the current period.
          *       == NUMA_PERIOD_THRESHOLD scan period stays the same
          *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
          *       >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
          */
         period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
         lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
         ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
 
         if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
                 /*
                  * Most memory accesses are local. There is no need to
                  * do fast NUMA scanning, since memory is already local.
                  */
                 int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
                 if (!slot)
                         slot = 1;
                 diff = slot * period_slot;
         } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
                 /*
                  * Most memory accesses are shared with other tasks.
                  * There is no point in continuing fast NUMA scanning,
                  * since other tasks may just move the memory elsewhere.
                  */
                 int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
                 if (!slot)
                         slot = 1;
                 diff = slot * period_slot;
         } else {
                 /*
                  * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
                  * yet they are not on the local NUMA node. Speed up
                  * NUMA scanning to get the memory moved over.
                  */
                 int ratio = max(lr_ratio, ps_ratio);
                 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
         }
 
         p->numa_scan_period = clamp(p->numa_scan_period + diff,
                         task_scan_min(p), task_scan_max(p));
         memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
 }
 
 /*
  * Get the fraction of time the task has been running since the last
  * NUMA placement cycle. The scheduler keeps similar statistics, but
  * decays those on a 32ms period, which is orders of magnitude off
  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
  * stats only if the task is so new there are no NUMA statistics yet.
  */
 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
 {
         u64 runtime, delta, now;
         /* Use the start of this time slice to avoid calculations. */
         now = p->se.exec_start;
         runtime = p->se.sum_exec_runtime;
 
         if (p->last_task_numa_placement) {
                 delta = runtime - p->last_sum_exec_runtime;
                 *period = now - p->last_task_numa_placement;
         } else {
                 delta = p->se.avg.load_sum;
                 *period = LOAD_AVG_MAX;
         }
 
         p->last_sum_exec_runtime = runtime;
         p->last_task_numa_placement = now;
 
         return delta;
 }
 
 /*
  * Determine the preferred nid for a task in a numa_group. This needs to
  * be done in a way that produces consistent results with group_weight,
  * otherwise workloads might not converge.
  */
 static int preferred_group_nid(struct task_struct *p, int nid)
 {
         nodemask_t nodes;
         int dist;
 
         /* Direct connections between all NUMA nodes. */
         if (sched_numa_topology_type == NUMA_DIRECT)
                 return nid;
 
         /*
          * On a system with glueless mesh NUMA topology, group_weight
          * scores nodes according to the number of NUMA hinting faults on
          * both the node itself, and on nearby nodes.
          */
         if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
                 unsigned long score, max_score = 0;
                 int node, max_node = nid;
 
                 dist = sched_max_numa_distance;
 
                 for_each_online_node(node) {
                         score = group_weight(p, node, dist);
                         if (score > max_score) {
                                 max_score = score;
                                 max_node = node;
                         }
                 }
                 return max_node;
         }
 
         /*
          * Finding the preferred nid in a system with NUMA backplane
          * interconnect topology is more involved. The goal is to locate
          * tasks from numa_groups near each other in the system, and
          * untangle workloads from different sides of the system. This requires
          * searching down the hierarchy of node groups, recursively searching
          * inside the highest scoring group of nodes. The nodemask tricks
          * keep the complexity of the search down.
          */
         nodes = node_online_map;
         for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
                 unsigned long max_faults = 0;
                 nodemask_t max_group = NODE_MASK_NONE;
                 int a, b;
 
                 /* Are there nodes at this distance from each other? */
                 if (!find_numa_distance(dist))
                         continue;
 
                 for_each_node_mask(a, nodes) {
                         unsigned long faults = 0;
                         nodemask_t this_group;
                         nodes_clear(this_group);
 
                         /* Sum group's NUMA faults; includes a==b case. */
                         for_each_node_mask(b, nodes) {
                                 if (node_distance(a, b) < dist) {
                                         faults += group_faults(p, b);
                                         node_set(b, this_group);
                                         node_clear(b, nodes);
                                 }
                         }
 
                         /* Remember the top group. */
                         if (faults > max_faults) {
                                 max_faults = faults;
                                 max_group = this_group;
                                 /*
                                  * subtle: at the smallest distance there is
                                  * just one node left in each "group", the
                                  * winner is the preferred nid.
                                  */
                                 nid = a;
                         }
                 }
                 /* Next round, evaluate the nodes within max_group. */
                 if (!max_faults)
                         break;
                 nodes = max_group;
         }
         return nid;
 }
 
 static void task_numa_placement(struct task_struct *p)
 {
         int seq, nid, max_nid = -1, max_group_nid = -1;
         unsigned long max_faults = 0, max_group_faults = 0;
         unsigned long fault_types[2] = { 0, 0 };
         unsigned long total_faults;
         u64 runtime, period;
         spinlock_t *group_lock = NULL;
 
         /*
          * The p->mm->numa_scan_seq field gets updated without
          * exclusive access. Use READ_ONCE() here to ensure
          * that the field is read in a single access:
          */
         seq = READ_ONCE(p->mm->numa_scan_seq);
         if (p->numa_scan_seq == seq)
                 return;
         p->numa_scan_seq = seq;
         p->numa_scan_period_max = task_scan_max(p);
 
         total_faults = p->numa_faults_locality[0] +
                        p->numa_faults_locality[1];
         runtime = numa_get_avg_runtime(p, &period);
 
         /* If the task is part of a group prevent parallel updates to group stats */
         if (p->numa_group) {
                 group_lock = &p->numa_group->lock;
                 spin_lock_irq(group_lock);
         }
 
         /* Find the node with the highest number of faults */
         for_each_online_node(nid) {
                 /* Keep track of the offsets in numa_faults array */
                 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
                 unsigned long faults = 0, group_faults = 0;
                 int priv;
 
                 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
                         long diff, f_diff, f_weight;
 
                         mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
                         membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
                         cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
                         cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
 
                         /* Decay existing window, copy faults since last scan */
                         diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
                         fault_types[priv] += p->numa_faults[membuf_idx];
                         p->numa_faults[membuf_idx] = 0;
 
                         /*
                          * Normalize the faults_from, so all tasks in a group
                          * count according to CPU use, instead of by the raw
                          * number of faults. Tasks with little runtime have
                          * little over-all impact on throughput, and thus their
                          * faults are less important.
                          */
                         f_weight = div64_u64(runtime << 16, period + 1);
                         f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
                                    (total_faults + 1);
                         f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
                         p->numa_faults[cpubuf_idx] = 0;
 
                         p->numa_faults[mem_idx] += diff;
                         p->numa_faults[cpu_idx] += f_diff;
                         faults += p->numa_faults[mem_idx];
                         p->total_numa_faults += diff;
                         if (p->numa_group) {
                                 /*
                                  * safe because we can only change our own group
                                  *
                                  * mem_idx represents the offset for a given
                                  * nid and priv in a specific region because it
                                  * is at the beginning of the numa_faults array.
                                  */
                                 p->numa_group->faults[mem_idx] += diff;
                                 p->numa_group->faults_cpu[mem_idx] += f_diff;
                                 p->numa_group->total_faults += diff;
                                 group_faults += p->numa_group->faults[mem_idx];
                         }
                 }
 
                 if (faults > max_faults) {
                         max_faults = faults;
                         max_nid = nid;
                 }
 
                 if (group_faults > max_group_faults) {
                         max_group_faults = group_faults;
                         max_group_nid = nid;
                 }
         }
 
         update_task_scan_period(p, fault_types[0], fault_types[1]);
 
         if (p->numa_group) {
                 numa_group_count_active_nodes(p->numa_group);
                 spin_unlock_irq(group_lock);
                 max_nid = preferred_group_nid(p, max_group_nid);
         }
 
         if (max_faults) {
                 /* Set the new preferred node */
                 if (max_nid != p->numa_preferred_nid)
                         sched_setnuma(p, max_nid);
 
                 if (task_node(p) != p->numa_preferred_nid)
                         numa_migrate_preferred(p);
         }
 }
 
 static inline int get_numa_group(struct numa_group *grp)
 {
         return atomic_inc_not_zero(&grp->refcount);
 }
 
 static inline void put_numa_group(struct numa_group *grp)
 {
         if (atomic_dec_and_test(&grp->refcount))
                 kfree_rcu(grp, rcu);
 }
 
 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
                         int *priv)
 {
         struct numa_group *grp, *my_grp;
         struct task_struct *tsk;
         bool join = false;
         int cpu = cpupid_to_cpu(cpupid);
         int i;
 
         if (unlikely(!p->numa_group)) {
                 unsigned int size = sizeof(struct numa_group) +
                                     4*nr_node_ids*sizeof(unsigned long);
 
                 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
                 if (!grp)
                         return;
 
                 atomic_set(&grp->refcount, 1);
                 grp->active_nodes = 1;
                 grp->max_faults_cpu = 0;
                 spin_lock_init(&grp->lock);
                 grp->gid = p->pid;
                 /* Second half of the array tracks nids where faults happen */
                 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
                                                 nr_node_ids;
 
                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
                         grp->faults[i] = p->numa_faults[i];
 
                 grp->total_faults = p->total_numa_faults;
 
                 grp->nr_tasks++;
                 rcu_assign_pointer(p->numa_group, grp);
         }
 
         rcu_read_lock();
         tsk = READ_ONCE(cpu_rq(cpu)->curr);
 
         if (!cpupid_match_pid(tsk, cpupid))
                 goto no_join;
 
         grp = rcu_dereference(tsk->numa_group);
         if (!grp)
                 goto no_join;
 
         my_grp = p->numa_group;
         if (grp == my_grp)
                 goto no_join;
 
         /*
          * Only join the other group if its bigger; if we're the bigger group,
          * the other task will join us.
          */
         if (my_grp->nr_tasks > grp->nr_tasks)
                 goto no_join;
 
         /*
          * Tie-break on the grp address.
          */
         if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
                 goto no_join;
 
         /* Always join threads in the same process. */
         if (tsk->mm == current->mm)
                 join = true;
 
         /* Simple filter to avoid false positives due to PID collisions */
         if (flags & TNF_SHARED)
                 join = true;
 
         /* Update priv based on whether false sharing was detected */
         *priv = !join;
 
         if (join && !get_numa_group(grp))
                 goto no_join;
 
         rcu_read_unlock();
 
         if (!join)
                 return;
 
         BUG_ON(irqs_disabled());
         double_lock_irq(&my_grp->lock, &grp->lock);
 
         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
                 my_grp->faults[i] -= p->numa_faults[i];
                 grp->faults[i] += p->numa_faults[i];
         }
         my_grp->total_faults -= p->total_numa_faults;
         grp->total_faults += p->total_numa_faults;
 
         my_grp->nr_tasks--;
         grp->nr_tasks++;
 
         spin_unlock(&my_grp->lock);
         spin_unlock_irq(&grp->lock);
 
         rcu_assign_pointer(p->numa_group, grp);
 
         put_numa_group(my_grp);
         return;
 
 no_join:
         rcu_read_unlock();
         return;
 }
 
 void task_numa_free(struct task_struct *p)
 {
         struct numa_group *grp = p->numa_group;
         void *numa_faults = p->numa_faults;
         unsigned long flags;
         int i;
 
         if (grp) {
                 spin_lock_irqsave(&grp->lock, flags);
                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
                         grp->faults[i] -= p->numa_faults[i];
                 grp->total_faults -= p->total_numa_faults;
 
                 grp->nr_tasks--;
                 spin_unlock_irqrestore(&grp->lock, flags);
                 RCU_INIT_POINTER(p->numa_group, NULL);
                 put_numa_group(grp);
         }
 
         p->numa_faults = NULL;
         kfree(numa_faults);
 }
 
 /*
  * Got a PROT_NONE fault for a page on @node.
  */
 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
 {
         struct task_struct *p = current;
         bool migrated = flags & TNF_MIGRATED;
         int cpu_node = task_node(current);
         int local = !!(flags & TNF_FAULT_LOCAL);
         struct numa_group *ng;
         int priv;
 
         if (!static_branch_likely(&sched_numa_balancing))
                 return;
 
         /* for example, ksmd faulting in a user's mm */
         if (!p->mm)
                 return;
 
         /* Allocate buffer to track faults on a per-node basis */
         if (unlikely(!p->numa_faults)) {
                 int size = sizeof(*p->numa_faults) *
                            NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
 
                 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
                 if (!p->numa_faults)
                         return;
 
                 p->total_numa_faults = 0;
                 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
         }
 
         /*
          * First accesses are treated as private, otherwise consider accesses
          * to be private if the accessing pid has not changed
          */
         if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
                 priv = 1;
         } else {
                 priv = cpupid_match_pid(p, last_cpupid);
                 if (!priv && !(flags & TNF_NO_GROUP))
                         task_numa_group(p, last_cpupid, flags, &priv);
         }
 
         /*
          * If a workload spans multiple NUMA nodes, a shared fault that
          * occurs wholly within the set of nodes that the workload is
          * actively using should be counted as local. This allows the
          * scan rate to slow down when a workload has settled down.
          */
         ng = p->numa_group;
         if (!priv && !local && ng && ng->active_nodes > 1 &&
                                 numa_is_active_node(cpu_node, ng) &&
                                 numa_is_active_node(mem_node, ng))
                 local = 1;
 
         task_numa_placement(p);
 
         /*
          * Retry task to preferred node migration periodically, in case it
          * case it previously failed, or the scheduler moved us.
          */
         if (time_after(jiffies, p->numa_migrate_retry))
                 numa_migrate_preferred(p);
 
         if (migrated)
                 p->numa_pages_migrated += pages;
         if (flags & TNF_MIGRATE_FAIL)
                 p->numa_faults_locality[2] += pages;
 
         p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
         p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
         p->numa_faults_locality[local] += pages;
 }
 
 static void reset_ptenuma_scan(struct task_struct *p)
 {
         /*
          * We only did a read acquisition of the mmap sem, so
          * p->mm->numa_scan_seq is written to without exclusive access
          * and the update is not guaranteed to be atomic. That's not
          * much of an issue though, since this is just used for
          * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
          * expensive, to avoid any form of compiler optimizations:
          */
         WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
         p->mm->numa_scan_offset = 0;
 }
 
 /*
  * The expensive part of numa migration is done from task_work context.
  * Triggered from task_tick_numa().
  */
 void task_numa_work(struct callback_head *work)
 {
         unsigned long migrate, next_scan, now = jiffies;
         struct task_struct *p = current;
         struct mm_struct *mm = p->mm;
         u64 runtime = p->se.sum_exec_runtime;
         struct vm_area_struct *vma;
         unsigned long start, end;
         unsigned long nr_pte_updates = 0;
         long pages, virtpages;
 
         SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
 
         work->next = work; /* protect against double add */
         /*
          * Who cares about NUMA placement when they're dying.
          *
          * NOTE: make sure not to dereference p->mm before this check,
          * exit_task_work() happens _after_ exit_mm() so we could be called
          * without p->mm even though we still had it when we enqueued this
          * work.
          */
         if (p->flags & PF_EXITING)
                 return;
 
         if (!mm->numa_next_scan) {
                 mm->numa_next_scan = now +
                         msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
         }
 
         /*
          * Enforce maximal scan/migration frequency..
          */
         migrate = mm->numa_next_scan;
         if (time_before(now, migrate))
                 return;
 
         if (p->numa_scan_period == 0) {
                 p->numa_scan_period_max = task_scan_max(p);
                 p->numa_scan_period = task_scan_start(p);
         }
 
         next_scan = now + msecs_to_jiffies(p->numa_scan_period);
         if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
                 return;
 
         /*
          * Delay this task enough that another task of this mm will likely win
          * the next time around.
          */
         p->node_stamp += 2 * TICK_NSEC;
 
         start = mm->numa_scan_offset;
         pages = sysctl_numa_balancing_scan_size;
         pages <<= 20 - PAGE_SHIFT; /* MB in pages */
         virtpages = pages * 8;     /* Scan up to this much virtual space */
         if (!pages)
                 return;
 
 
         if (!down_read_trylock(&mm->mmap_sem))
                 return;
         vma = find_vma(mm, start);
         if (!vma) {
                 reset_ptenuma_scan(p);
                 start = 0;
                 vma = mm->mmap;
         }
         for (; vma; vma = vma->vm_next) {
                 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
                         is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
                         continue;
                 }
 
                 /*
                  * Shared library pages mapped by multiple processes are not
                  * migrated as it is expected they are cache replicated. Avoid
                  * hinting faults in read-only file-backed mappings or the vdso
                  * as migrating the pages will be of marginal benefit.
                  */
                 if (!vma->vm_mm ||
                     (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
                         continue;
 
                 /*
                  * Skip inaccessible VMAs to avoid any confusion between
                  * PROT_NONE and NUMA hinting ptes
                  */
                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
                         continue;
 
                 do {
                         start = max(start, vma->vm_start);
                         end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
                         end = min(end, vma->vm_end);
                         nr_pte_updates = change_prot_numa(vma, start, end);
 
                         /*
                          * Try to scan sysctl_numa_balancing_size worth of
                          * hpages that have at least one present PTE that
                          * is not already pte-numa. If the VMA contains
                          * areas that are unused or already full of prot_numa
                          * PTEs, scan up to virtpages, to skip through those
                          * areas faster.
                          */
                         if (nr_pte_updates)
                                 pages -= (end - start) >> PAGE_SHIFT;
                         virtpages -= (end - start) >> PAGE_SHIFT;
 
                         start = end;
                         if (pages <= 0 || virtpages <= 0)
                                 goto out;
 
                         cond_resched();
                 } while (end != vma->vm_end);
         }
 
 out:
         /*
          * It is possible to reach the end of the VMA list but the last few
          * VMAs are not guaranteed to the vma_migratable. If they are not, we
          * would find the !migratable VMA on the next scan but not reset the
          * scanner to the start so check it now.
          */
         if (vma)
                 mm->numa_scan_offset = start;
         else
                 reset_ptenuma_scan(p);
         up_read(&mm->mmap_sem);
 
         /*
          * Make sure tasks use at least 32x as much time to run other code
          * than they used here, to limit NUMA PTE scanning overhead to 3% max.
          * Usually update_task_scan_period slows down scanning enough; on an
          * overloaded system we need to limit overhead on a per task basis.
          */
         if (unlikely(p->se.sum_exec_runtime != runtime)) {
                 u64 diff = p->se.sum_exec_runtime - runtime;
                 p->node_stamp += 32 * diff;
         }
 }
 
 /*
  * Drive the periodic memory faults..
  */
 void task_tick_numa(struct rq *rq, struct task_struct *curr)
 {
         struct callback_head *work = &curr->numa_work;
         u64 period, now;
 
         /*
          * We don't care about NUMA placement if we don't have memory.
          */
         if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
                 return;
 
         /*
          * Using runtime rather than walltime has the dual advantage that
          * we (mostly) drive the selection from busy threads and that the
          * task needs to have done some actual work before we bother with
          * NUMA placement.
          */
         now = curr->se.sum_exec_runtime;
         period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
 
         if (now > curr->node_stamp + period) {
                 if (!curr->node_stamp)
                         curr->numa_scan_period = task_scan_start(curr);
                 curr->node_stamp += period;
 
                 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
                         init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
                         task_work_add(curr, work, true);
                 }
         }
 }
 
 #else
 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
 {
 }
 
 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
 {
 }
 
 #endif /* CONFIG_NUMA_BALANCING */
 
 static void
 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         update_load_add(&cfs_rq->load, se->load.weight);
         if (!parent_entity(se))
                 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
 #ifdef CONFIG_SMP
         if (entity_is_task(se)) {
                 struct rq *rq = rq_of(cfs_rq);
 
                 account_numa_enqueue(rq, task_of(se));
                 list_add(&se->group_node, &rq->cfs_tasks);
         }
 #endif
         cfs_rq->nr_running++;
 }
 
 static void
 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         update_load_sub(&cfs_rq->load, se->load.weight);
         if (!parent_entity(se))
                 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
 #ifdef CONFIG_SMP
         if (entity_is_task(se)) {
                 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
                 list_del_init(&se->group_node);
         }
 #endif
         cfs_rq->nr_running--;
 }
 
 /*
  * Signed add and clamp on underflow.
  *
  * Explicitly do a load-store to ensure the intermediate value never hits
  * memory. This allows lockless observations without ever seeing the negative
  * values.
  */
 #define add_positive(_ptr, _val) do {                           \
         typeof(_ptr) ptr = (_ptr);                              \
         typeof(_val) val = (_val);                              \
         typeof(*ptr) res, var = READ_ONCE(*ptr);                \
                                                                 \
         res = var + val;                                        \
                                                                 \
         if (val < 0 && res > var)                               \
                 res = 0;                                        \
                                                                 \
         WRITE_ONCE(*ptr, res);                                  \
 } while (0)
 
 /*
  * Unsigned subtract and clamp on underflow.
  *
  * Explicitly do a load-store to ensure the intermediate value never hits
  * memory. This allows lockless observations without ever seeing the negative
  * values.
  */
 #define sub_positive(_ptr, _val) do {                           \
         typeof(_ptr) ptr = (_ptr);                              \
         typeof(*ptr) val = (_val);                              \
         typeof(*ptr) res, var = READ_ONCE(*ptr);                \
         res = var - val;                                        \
         if (res > var)                                          \
                 res = 0;                                        \
         WRITE_ONCE(*ptr, res);                                  \
 } while (0)
 
 #ifdef CONFIG_SMP
 /*
  * XXX we want to get rid of these helpers and use the full load resolution.
  */
 static inline long se_weight(struct sched_entity *se)
 {
         return scale_load_down(se->load.weight);
 }
 
 static inline long se_runnable(struct sched_entity *se)
 {
         return scale_load_down(se->runnable_weight);
 }
 
 static inline void
 enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         cfs_rq->runnable_weight += se->runnable_weight;
 
         cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
         cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
 }
 
 static inline void
 dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         cfs_rq->runnable_weight -= se->runnable_weight;
 
         sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
         sub_positive(&cfs_rq->avg.runnable_load_sum,
                      se_runnable(se) * se->avg.runnable_load_sum);
 }
 
 static inline void
 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         cfs_rq->avg.load_avg += se->avg.load_avg;
         cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
 }
 
 static inline void
 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
         sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
 }
 #else
 static inline void
 enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 static inline void
 dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 static inline void
 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 static inline void
 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 #endif
 
 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
                             unsigned long weight, unsigned long runnable)
 {
         if (se->on_rq) {
                 /* commit outstanding execution time */
                 if (cfs_rq->curr == se)
                         update_curr(cfs_rq);
                 account_entity_dequeue(cfs_rq, se);
                 dequeue_runnable_load_avg(cfs_rq, se);
         }
         dequeue_load_avg(cfs_rq, se);
 
         se->runnable_weight = runnable;
         update_load_set(&se->load, weight);
 
 #ifdef CONFIG_SMP
         do {
                 u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
 
                 se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
                 se->avg.runnable_load_avg =
                         div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
         } while (0);
 #endif
 
         enqueue_load_avg(cfs_rq, se);
         if (se->on_rq) {
                 account_entity_enqueue(cfs_rq, se);
                 enqueue_runnable_load_avg(cfs_rq, se);
         }
 }
 
 void reweight_task(struct task_struct *p, int prio)
 {
         struct sched_entity *se = &p->se;
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         struct load_weight *load = &se->load;
         unsigned long weight = scale_load(sched_prio_to_weight[prio]);
 
         reweight_entity(cfs_rq, se, weight, weight);
         load->inv_weight = sched_prio_to_wmult[prio];
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_SMP
 /*
  * All this does is approximate the hierarchical proportion which includes that
  * global sum we all love to hate.
  *
  * That is, the weight of a group entity, is the proportional share of the
  * group weight based on the group runqueue weights. That is:
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = -----------------------------               (1)
  *                        \Sum grq->load.weight
  *
  * Now, because computing that sum is prohibitively expensive to compute (been
  * there, done that) we approximate it with this average stuff. The average
  * moves slower and therefore the approximation is cheaper and more stable.
  *
  * So instead of the above, we substitute:
  *
  *   grq->load.weight -> grq->avg.load_avg                         (2)
  *
  * which yields the following:
  *
  *                     tg->weight * grq->avg.load_avg
  *   ge->load.weight = ------------------------------              (3)
  *                              tg->load_avg
  *
  * Where: tg->load_avg ~= \Sum grq->avg.load_avg
  *
  * That is shares_avg, and it is right (given the approximation (2)).
  *
  * The problem with it is that because the average is slow -- it was designed
  * to be exactly that of course -- this leads to transients in boundary
  * conditions. In specific, the case where the group was idle and we start the
  * one task. It takes time for our CPU's grq->avg.load_avg to build up,
  * yielding bad latency etc..
  *
  * Now, in that special case (1) reduces to:
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = ----------------------------- = tg->weight   (4)
  *                          grp->load.weight
  *
  * That is, the sum collapses because all other CPUs are idle; the UP scenario.
  *
  * So what we do is modify our approximation (3) to approach (4) in the (near)
  * UP case, like:
  *
  *   ge->load.weight =
  *
  *              tg->weight * grq->load.weight
  *     ---------------------------------------------------         (5)
  *     tg->load_avg - grq->avg.load_avg + grq->load.weight
  *
  * But because grq->load.weight can drop to 0, resulting in a divide by zero,
  * we need to use grq->avg.load_avg as its lower bound, which then gives:
  *
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = -----------------------------               (6)
  *                              tg_load_avg'
  *
  * Where:
  *
  *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
  *                  max(grq->load.weight, grq->avg.load_avg)
  *
  * And that is shares_weight and is icky. In the (near) UP case it approaches
  * (4) while in the normal case it approaches (3). It consistently
  * overestimates the ge->load.weight and therefore:
  *
  *   \Sum ge->load.weight >= tg->weight
  *
  * hence icky!
  */
 static long calc_group_shares(struct cfs_rq *cfs_rq)
 {
         long tg_weight, tg_shares, load, shares;
         struct task_group *tg = cfs_rq->tg;
 
         tg_shares = READ_ONCE(tg->shares);
 
         load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
 
         tg_weight = atomic_long_read(&tg->load_avg);
 
         /* Ensure tg_weight >= load */
         tg_weight -= cfs_rq->tg_load_avg_contrib;
         tg_weight += load;
 
         shares = (tg_shares * load);
         if (tg_weight)
                 shares /= tg_weight;
 
         /*
          * MIN_SHARES has to be unscaled here to support per-CPU partitioning
          * of a group with small tg->shares value. It is a floor value which is
          * assigned as a minimum load.weight to the sched_entity representing
          * the group on a CPU.
          *
          * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
          * on an 8-core system with 8 tasks each runnable on one CPU shares has
          * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
          * case no task is runnable on a CPU MIN_SHARES=2 should be returned
          * instead of 0.
          */
         return clamp_t(long, shares, MIN_SHARES, tg_shares);
 }
 
 /*
  * This calculates the effective runnable weight for a group entity based on
  * the group entity weight calculated above.
  *
  * Because of the above approximation (2), our group entity weight is
  * an load_avg based ratio (3). This means that it includes blocked load and
  * does not represent the runnable weight.
  *
  * Approximate the group entity's runnable weight per ratio from the group
  * runqueue:
  *
  *                                           grq->avg.runnable_load_avg
  *   ge->runnable_weight = ge->load.weight * -------------------------- (7)
  *                                               grq->avg.load_avg
  *
  * However, analogous to above, since the avg numbers are slow, this leads to
  * transients in the from-idle case. Instead we use:
  *
  *   ge->runnable_weight = ge->load.weight *
  *
  *              max(grq->avg.runnable_load_avg, grq->runnable_weight)
  *              -----------------------------------------------------   (8)
  *                    max(grq->avg.load_avg, grq->load.weight)
  *
  * Where these max() serve both to use the 'instant' values to fix the slow
  * from-idle and avoid the /0 on to-idle, similar to (6).
  */
 static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
 {
         long runnable, load_avg;
 
         load_avg = max(cfs_rq->avg.load_avg,
                        scale_load_down(cfs_rq->load.weight));
 
         runnable = max(cfs_rq->avg.runnable_load_avg,
                        scale_load_down(cfs_rq->runnable_weight));
 
         runnable *= shares;
         if (load_avg)
                 runnable /= load_avg;
 
         return clamp_t(long, runnable, MIN_SHARES, shares);
 }
 #endif /* CONFIG_SMP */
 
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
 
 /*
  * Recomputes the group entity based on the current state of its group
  * runqueue.
  */
 static void update_cfs_group(struct sched_entity *se)
 {
         struct cfs_rq *gcfs_rq = group_cfs_rq(se);
         long shares, runnable;
 
         if (!gcfs_rq)
                 return;
 
         if (throttled_hierarchy(gcfs_rq))
                 return;
 
 #ifndef CONFIG_SMP
         runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
 
         if (likely(se->load.weight == shares))
                 return;
 #else
         shares   = calc_group_shares(gcfs_rq);
         runnable = calc_group_runnable(gcfs_rq, shares);
 #endif
 
         reweight_entity(cfs_rq_of(se), se, shares, runnable);
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */
 static inline void update_cfs_group(struct sched_entity *se)
 {
 }
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
 {
         struct rq *rq = rq_of(cfs_rq);
 
         if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
                 /*
                  * There are a few boundary cases this might miss but it should
                  * get called often enough that that should (hopefully) not be
                  * a real problem.
                  *
                  * It will not get called when we go idle, because the idle
                  * thread is a different class (!fair), nor will the utilization
                  * number include things like RT tasks.
                  *
                  * As is, the util number is not freq-invariant (we'd have to
                  * implement arch_scale_freq_capacity() for that).
                  *
                  * See cpu_util().
                  */
                 cpufreq_update_util(rq, flags);
         }
 }
 
 #ifdef CONFIG_SMP
 /*
  * Approximate:
  *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
  */
 static u64 decay_load(u64 val, u64 n)
 {
         unsigned int local_n;
 
         if (unlikely(n > LOAD_AVG_PERIOD * 63))
                 return 0;
 
         /* after bounds checking we can collapse to 32-bit */
         local_n = n;
 
         /*
          * As y^PERIOD = 1/2, we can combine
          *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
          * With a look-up table which covers y^n (n<PERIOD)
          *
          * To achieve constant time decay_load.
          */
         if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
                 val >>= local_n / LOAD_AVG_PERIOD;
                 local_n %= LOAD_AVG_PERIOD;
         }
 
         val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
         return val;
 }
 
 static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
 {
         u32 c1, c2, c3 = d3; /* y^0 == 1 */
 
         /*
          * c1 = d1 y^p
          */
         c1 = decay_load((u64)d1, periods);
 
         /*
          *            p-1
          * c2 = 1024 \Sum y^n
          *            n=1
          *
          *              inf        inf
          *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
          *              n=0        n=p
          */
         c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
 
         return c1 + c2 + c3;
 }
 
 /*
  * Accumulate the three separate parts of the sum; d1 the remainder
  * of the last (incomplete) period, d2 the span of full periods and d3
  * the remainder of the (incomplete) current period.
  *
  *           d1          d2           d3
  *           ^           ^            ^
  *           |           |            |
  *         |<->|<----------------->|<--->|
  * ... |---x---|------| ... |------|-----x (now)
  *
  *                           p-1
  * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
  *                           n=1
  *
  *    = u y^p +                                 (Step 1)
  *
  *                     p-1
  *      d1 y^p + 1024 \Sum y^n + d3 y^0         (Step 2)
  *                     n=1
  */
 static __always_inline u32
 accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
                unsigned long load, unsigned long runnable, int running)
 {
         unsigned long scale_freq, scale_cpu;
         u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
         u64 periods;
 
         scale_freq = arch_scale_freq_capacity(cpu);
         scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
 
         delta += sa->period_contrib;
         periods = delta / 1024; /* A period is 1024us (~1ms) */
 
         /*
          * Step 1: decay old *_sum if we crossed period boundaries.
          */
         if (periods) {
                 sa->load_sum = decay_load(sa->load_sum, periods);
                 sa->runnable_load_sum =
                         decay_load(sa->runnable_load_sum, periods);
                 sa->util_sum = decay_load((u64)(sa->util_sum), periods);
 
                 /*
                  * Step 2
                  */
                 delta %= 1024;
                 contrib = __accumulate_pelt_segments(periods,
                                 1024 - sa->period_contrib, delta);
         }
         sa->period_contrib = delta;
 
         contrib = cap_scale(contrib, scale_freq);
         if (load)
                 sa->load_sum += load * contrib;
         if (runnable)
                 sa->runnable_load_sum += runnable * contrib;
         if (running)
                 sa->util_sum += contrib * scale_cpu;
 
         return periods;
 }
 
 /*
  * We can represent the historical contribution to runnable average as the
  * coefficients of a geometric series.  To do this we sub-divide our runnable
  * history into segments of approximately 1ms (1024us); label the segment that
  * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
  *
  * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
  *      p0            p1           p2
  *     (now)       (~1ms ago)  (~2ms ago)
  *
  * Let u_i denote the fraction of p_i that the entity was runnable.
  *
  * We then designate the fractions u_i as our co-efficients, yielding the
  * following representation of historical load:
  *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
  *
  * We choose y based on the with of a reasonably scheduling period, fixing:
  *   y^32 = 0.5
  *
  * This means that the contribution to load ~32ms ago (u_32) will be weighted
  * approximately half as much as the contribution to load within the last ms
  * (u_0).
  *
  * When a period "rolls over" and we have new u_0`, multiplying the previous
  * sum again by y is sufficient to update:
  *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
  *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
  */
 static __always_inline int
 ___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
                   unsigned long load, unsigned long runnable, int running)
 {
         u64 delta;
 
         delta = now - sa->last_update_time;
         /*
          * This should only happen when time goes backwards, which it
          * unfortunately does during sched clock init when we swap over to TSC.
          */
         if ((s64)delta < 0) {
                 sa->last_update_time = now;
                 return 0;
         }
 
         /*
          * Use 1024ns as the unit of measurement since it's a reasonable
          * approximation of 1us and fast to compute.
          */
         delta >>= 10;
         if (!delta)
                 return 0;
 
         sa->last_update_time += delta << 10;
 
         /*
          * running is a subset of runnable (weight) so running can't be set if
          * runnable is clear. But there are some corner cases where the current
          * se has been already dequeued but cfs_rq->curr still points to it.
          * This means that weight will be 0 but not running for a sched_entity
          * but also for a cfs_rq if the latter becomes idle. As an example,
          * this happens during idle_balance() which calls
          * update_blocked_averages()
          */
         if (!load)
                 runnable = running = 0;
 
         /*
          * Now we know we crossed measurement unit boundaries. The *_avg
          * accrues by two steps:
          *
          * Step 1: accumulate *_sum since last_update_time. If we haven't
          * crossed period boundaries, finish.
          */
         if (!accumulate_sum(delta, cpu, sa, load, runnable, running))
                 return 0;
 
         return 1;
 }
 
 static __always_inline void
 ___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
 {
         u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
 
         /*
          * Step 2: update *_avg.
          */
         sa->load_avg = div_u64(load * sa->load_sum, divider);
         sa->runnable_load_avg = div_u64(runnable * sa->runnable_load_sum, divider);
         sa->util_avg = sa->util_sum / divider;
 }
 
 /*
  * When a task is dequeued, its estimated utilization should not be update if
  * its util_avg has not been updated at least once.
  * This flag is used to synchronize util_avg updates with util_est updates.
  * We map this information into the LSB bit of the utilization saved at
  * dequeue time (i.e. util_est.dequeued).
  */
 #define UTIL_AVG_UNCHANGED 0x1
 
 static inline void cfs_se_util_change(struct sched_avg *avg)
 {
         unsigned int enqueued;
 
         if (!sched_feat(UTIL_EST))
                 return;
 
         /* Avoid store if the flag has been already set */
         enqueued = avg->util_est.enqueued;
         if (!(enqueued & UTIL_AVG_UNCHANGED))
                 return;
 
         /* Reset flag to report util_avg has been updated */
         enqueued &= ~UTIL_AVG_UNCHANGED;
         WRITE_ONCE(avg->util_est.enqueued, enqueued);
 }
 
 /*
  * sched_entity:
  *
  *   task:
  *     se_runnable() == se_weight()
  *
  *   group: [ see update_cfs_group() ]
  *     se_weight()   = tg->weight * grq->load_avg / tg->load_avg
  *     se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
  *
  *   load_sum := runnable_sum
  *   load_avg = se_weight(se) * runnable_avg
  *
  *   runnable_load_sum := runnable_sum
  *   runnable_load_avg = se_runnable(se) * runnable_avg
  *
  * XXX collapse load_sum and runnable_load_sum
  *
  * cfq_rs:
  *
  *   load_sum = \Sum se_weight(se) * se->avg.load_sum
  *   load_avg = \Sum se->avg.load_avg
  *
  *   runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
  *   runnable_load_avg = \Sum se->avg.runable_load_avg
  */
 
 static int
 __update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
 {
         if (entity_is_task(se))
                 se->runnable_weight = se->load.weight;
 
         if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) {
                 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
                 return 1;
         }
 
         return 0;
 }
 
 static int
 __update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         if (entity_is_task(se))
                 se->runnable_weight = se->load.weight;
 
         if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq,
                                 cfs_rq->curr == se)) {
 
                 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
                 cfs_se_util_change(&se->avg);
                 return 1;
         }
 
         return 0;
 }
 
 static int
 __update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
 {
         if (___update_load_sum(now, cpu, &cfs_rq->avg,
                                 scale_load_down(cfs_rq->load.weight),
                                 scale_load_down(cfs_rq->runnable_weight),
                                 cfs_rq->curr != NULL)) {
 
                 ___update_load_avg(&cfs_rq->avg, 1, 1);
                 return 1;
         }
 
         return 0;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /**
  * update_tg_load_avg - update the tg's load avg
  * @cfs_rq: the cfs_rq whose avg changed
  * @force: update regardless of how small the difference
  *
  * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
  * However, because tg->load_avg is a global value there are performance
  * considerations.
  *
  * In order to avoid having to look at the other cfs_rq's, we use a
  * differential update where we store the last value we propagated. This in
  * turn allows skipping updates if the differential is 'small'.
  *
  * Updating tg's load_avg is necessary before update_cfs_share().
  */
 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
 {
         long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
 
         /*
          * No need to update load_avg for root_task_group as it is not used.
          */
         if (cfs_rq->tg == &root_task_group)
                 return;
 
         if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
                 atomic_long_add(delta, &cfs_rq->tg->load_avg);
                 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
         }
 }
 
 /*
  * Called within set_task_rq() right before setting a task's CPU. The
  * caller only guarantees p->pi_lock is held; no other assumptions,
  * including the state of rq->lock, should be made.
  */
 void set_task_rq_fair(struct sched_entity *se,
                       struct cfs_rq *prev, struct cfs_rq *next)
 {
         u64 p_last_update_time;
         u64 n_last_update_time;
 
         if (!sched_feat(ATTACH_AGE_LOAD))
                 return;
 
         /*
          * We are supposed to update the task to "current" time, then its up to
          * date and ready to go to new CPU/cfs_rq. But we have difficulty in
          * getting what current time is, so simply throw away the out-of-date
          * time. This will result in the wakee task is less decayed, but giving
          * the wakee more load sounds not bad.
          */
         if (!(se->avg.last_update_time && prev))
                 return;
 
 #ifndef CONFIG_64BIT
         {
                 u64 p_last_update_time_copy;
                 u64 n_last_update_time_copy;
 
                 do {
                         p_last_update_time_copy = prev->load_last_update_time_copy;
                         n_last_update_time_copy = next->load_last_update_time_copy;
 
                         smp_rmb();
 
                         p_last_update_time = prev->avg.last_update_time;
                         n_last_update_time = next->avg.last_update_time;
 
                 } while (p_last_update_time != p_last_update_time_copy ||
                          n_last_update_time != n_last_update_time_copy);
         }
 #else
         p_last_update_time = prev->avg.last_update_time;
         n_last_update_time = next->avg.last_update_time;
 #endif
         __update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
         se->avg.last_update_time = n_last_update_time;
 }
 
 
 /*
  * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
  * propagate its contribution. The key to this propagation is the invariant
  * that for each group:
  *
  *   ge->avg == grq->avg                                                (1)
  *
  * _IFF_ we look at the pure running and runnable sums. Because they
  * represent the very same entity, just at different points in the hierarchy.
  *
  * Per the above update_tg_cfs_util() is trivial and simply copies the running
  * sum over (but still wrong, because the group entity and group rq do not have
  * their PELT windows aligned).
  *
  * However, update_tg_cfs_runnable() is more complex. So we have:
  *
  *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg          (2)
  *
  * And since, like util, the runnable part should be directly transferable,
  * the following would _appear_ to be the straight forward approach:
  *
  *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg       (3)
  *
  * And per (1) we have:
  *
  *   ge->avg.runnable_avg == grq->avg.runnable_avg
  *
  * Which gives:
  *
  *                      ge->load.weight * grq->avg.load_avg
  *   ge->avg.load_avg = -----------------------------------             (4)
  *                               grq->load.weight
  *
  * Except that is wrong!
  *
  * Because while for entities historical weight is not important and we
  * really only care about our future and therefore can consider a pure
  * runnable sum, runqueues can NOT do this.
  *
  * We specifically want runqueues to have a load_avg that includes
  * historical weights. Those represent the blocked load, the load we expect
  * to (shortly) return to us. This only works by keeping the weights as
  * integral part of the sum. We therefore cannot decompose as per (3).
  *
  * Another reason this doesn't work is that runnable isn't a 0-sum entity.
  * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
  * rq itself is runnable anywhere between 2/3 and 1 depending on how the
  * runnable section of these tasks overlap (or not). If they were to perfectly
  * align the rq as a whole would be runnable 2/3 of the time. If however we
  * always have at least 1 runnable task, the rq as a whole is always runnable.
  *
  * So we'll have to approximate.. :/
  *
  * Given the constraint:
  *
  *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
  *
  * We can construct a rule that adds runnable to a rq by assuming minimal
  * overlap.
  *
  * On removal, we'll assume each task is equally runnable; which yields:
  *
  *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
  *
  * XXX: only do this for the part of runnable > running ?
  *
  */
 
 static inline void
 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
         long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
 
         /* Nothing to update */
         if (!delta)
                 return;
 
         /*
          * The relation between sum and avg is:
          *
          *   LOAD_AVG_MAX - 1024 + sa->period_contrib
          *
          * however, the PELT windows are not aligned between grq and gse.
          */
 
         /* Set new sched_entity's utilization */
         se->avg.util_avg = gcfs_rq->avg.util_avg;
         se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
 
         /* Update parent cfs_rq utilization */
         add_positive(&cfs_rq->avg.util_avg, delta);
         cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
 }
 
 static inline void
 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
         long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
         unsigned long runnable_load_avg, load_avg;
         u64 runnable_load_sum, load_sum = 0;
         s64 delta_sum;
 
         if (!runnable_sum)
                 return;
 
         gcfs_rq->prop_runnable_sum = 0;
 
         if (runnable_sum >= 0) {
                 /*
                  * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
                  * the CPU is saturated running == runnable.
                  */
                 runnable_sum += se->avg.load_sum;
                 runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
         } else {
                 /*
                  * Estimate the new unweighted runnable_sum of the gcfs_rq by
                  * assuming all tasks are equally runnable.
                  */
                 if (scale_load_down(gcfs_rq->load.weight)) {
                         load_sum = div_s64(gcfs_rq->avg.load_sum,
                                 scale_load_down(gcfs_rq->load.weight));
                 }
 
                 /* But make sure to not inflate se's runnable */
                 runnable_sum = min(se->avg.load_sum, load_sum);
         }
 
         /*
          * runnable_sum can't be lower than running_sum
          * As running sum is scale with CPU capacity wehreas the runnable sum
          * is not we rescale running_sum 1st
          */
         running_sum = se->avg.util_sum /
                 arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
         runnable_sum = max(runnable_sum, running_sum);
 
         load_sum = (s64)se_weight(se) * runnable_sum;
         load_avg = div_s64(load_sum, LOAD_AVG_MAX);
 
         delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
         delta_avg = load_avg - se->avg.load_avg;
 
         se->avg.load_sum = runnable_sum;
         se->avg.load_avg = load_avg;
         add_positive(&cfs_rq->avg.load_avg, delta_avg);
         add_positive(&cfs_rq->avg.load_sum, delta_sum);
 
         runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
         runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
         delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
         delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
 
         se->avg.runnable_load_sum = runnable_sum;
         se->avg.runnable_load_avg = runnable_load_avg;
 
         if (se->on_rq) {
                 add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
                 add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
         }
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
 {
         cfs_rq->propagate = 1;
         cfs_rq->prop_runnable_sum += runnable_sum;
 }
 
 /* Update task and its cfs_rq load average */
 static inline int propagate_entity_load_avg(struct sched_entity *se)
 {
         struct cfs_rq *cfs_rq, *gcfs_rq;
 
         if (entity_is_task(se))
                 return 0;
 
         gcfs_rq = group_cfs_rq(se);
         if (!gcfs_rq->propagate)
                 return 0;
 
         gcfs_rq->propagate = 0;
 
         cfs_rq = cfs_rq_of(se);
 
         add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
 
         update_tg_cfs_util(cfs_rq, se, gcfs_rq);
         update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
 
         return 1;
 }
 
 /*
  * Check if we need to update the load and the utilization of a blocked
  * group_entity:
  */
 static inline bool skip_blocked_update(struct sched_entity *se)
 {
         struct cfs_rq *gcfs_rq = group_cfs_rq(se);
 
         /*
          * If sched_entity still have not zero load or utilization, we have to
          * decay it:
          */
         if (se->avg.load_avg || se->avg.util_avg)
                 return false;
 
         /*
          * If there is a pending propagation, we have to update the load and
          * the utilization of the sched_entity:
          */
         if (gcfs_rq->propagate)
                 return false;
 
         /*
          * Otherwise, the load and the utilization of the sched_entity is
          * already zero and there is no pending propagation, so it will be a
          * waste of time to try to decay it:
          */
         return true;
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
 
 static inline int propagate_entity_load_avg(struct sched_entity *se)
 {
         return 0;
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
 
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 /**
  * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
  * @now: current time, as per cfs_rq_clock_task()
  * @cfs_rq: cfs_rq to update
  *
  * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
  * avg. The immediate corollary is that all (fair) tasks must be attached, see
  * post_init_entity_util_avg().
  *
  * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
  *
  * Returns true if the load decayed or we removed load.
  *
  * Since both these conditions indicate a changed cfs_rq->avg.load we should
  * call update_tg_load_avg() when this function returns true.
  */
 static inline int
 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 {
         unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
         struct sched_avg *sa = &cfs_rq->avg;
         int decayed = 0;
 
         if (cfs_rq->removed.nr) {
                 unsigned long r;
                 u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
 
                 raw_spin_lock(&cfs_rq->removed.lock);
                 swap(cfs_rq->removed.util_avg, removed_util);
                 swap(cfs_rq->removed.load_avg, removed_load);
                 swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
                 cfs_rq->removed.nr = 0;
                 raw_spin_unlock(&cfs_rq->removed.lock);
 
                 r = removed_load;
                 sub_positive(&sa->load_avg, r);
                 sub_positive(&sa->load_sum, r * divider);
 
                 r = removed_util;
                 sub_positive(&sa->util_avg, r);
                 sub_positive(&sa->util_sum, r * divider);
 
                 add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
 
                 decayed = 1;
         }
 
         decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
 
 #ifndef CONFIG_64BIT
         smp_wmb();
         cfs_rq->load_last_update_time_copy = sa->last_update_time;
 #endif
 
         if (decayed)
                 cfs_rq_util_change(cfs_rq, 0);
 
         return decayed;
 }
 
 /**
  * attach_entity_load_avg - attach this entity to its cfs_rq load avg
  * @cfs_rq: cfs_rq to attach to
  * @se: sched_entity to attach
  *
  * Must call update_cfs_rq_load_avg() before this, since we rely on
  * cfs_rq->avg.last_update_time being current.
  */
 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
         u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
 
         /*
          * When we attach the @se to the @cfs_rq, we must align the decay
          * window because without that, really weird and wonderful things can
          * happen.
          *
          * XXX illustrate
          */
         se->avg.last_update_time = cfs_rq->avg.last_update_time;
         se->avg.period_contrib = cfs_rq->avg.period_contrib;
 
         /*
          * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
          * period_contrib. This isn't strictly correct, but since we're
          * entirely outside of the PELT hierarchy, nobody cares if we truncate
          * _sum a little.
          */
         se->avg.util_sum = se->avg.util_avg * divider;
 
         se->avg.load_sum = divider;
         if (se_weight(se)) {
                 se->avg.load_sum =
                         div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
         }
 
         se->avg.runnable_load_sum = se->avg.load_sum;
 
         enqueue_load_avg(cfs_rq, se);
         cfs_rq->avg.util_avg += se->avg.util_avg;
         cfs_rq->avg.util_sum += se->avg.util_sum;
 
         add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
 
         cfs_rq_util_change(cfs_rq, flags);
 }
 
 /**
  * detach_entity_load_avg - detach this entity from its cfs_rq load avg
  * @cfs_rq: cfs_rq to detach from
  * @se: sched_entity to detach
  *
  * Must call update_cfs_rq_load_avg() before this, since we rely on
  * cfs_rq->avg.last_update_time being current.
  */
 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         dequeue_load_avg(cfs_rq, se);
         sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
         sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
 
         add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
 
         cfs_rq_util_change(cfs_rq, 0);
 }
 
 /*
  * Optional action to be done while updating the load average
  */
 #define UPDATE_TG       0x1
 #define SKIP_AGE_LOAD   0x2
 #define DO_ATTACH       0x4
 
 /* Update task and its cfs_rq load average */
 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
         u64 now = cfs_rq_clock_task(cfs_rq);
         struct rq *rq = rq_of(cfs_rq);
         int cpu = cpu_of(rq);
         int decayed;
 
         /*
          * Track task load average for carrying it to new CPU after migrated, and
          * track group sched_entity load average for task_h_load calc in migration
          */
         if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
                 __update_load_avg_se(now, cpu, cfs_rq, se);
 
         decayed  = update_cfs_rq_load_avg(now, cfs_rq);
         decayed |= propagate_entity_load_avg(se);
 
         if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
 
                 /*
                  * DO_ATTACH means we're here from enqueue_entity().
                  * !last_update_time means we've passed through
                  * migrate_task_rq_fair() indicating we migrated.
                  *
                  * IOW we're enqueueing a task on a new CPU.
                  */
                 attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
                 update_tg_load_avg(cfs_rq, 0);
 
         } else if (decayed && (flags & UPDATE_TG))
                 update_tg_load_avg(cfs_rq, 0);
 }
 
 #ifndef CONFIG_64BIT
 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
 {
         u64 last_update_time_copy;
         u64 last_update_time;
 
         do {
                 last_update_time_copy = cfs_rq->load_last_update_time_copy;
                 smp_rmb();
                 last_update_time = cfs_rq->avg.last_update_time;
         } while (last_update_time != last_update_time_copy);
 
         return last_update_time;
 }
 #else
 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
 {
         return cfs_rq->avg.last_update_time;
 }
 #endif
 
 /*
  * Synchronize entity load avg of dequeued entity without locking
  * the previous rq.
  */
 void sync_entity_load_avg(struct sched_entity *se)
 {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         u64 last_update_time;
 
         last_update_time = cfs_rq_last_update_time(cfs_rq);
         __update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
 }
 
 /*
  * Task first catches up with cfs_rq, and then subtract
  * itself from the cfs_rq (task must be off the queue now).
  */
 void remove_entity_load_avg(struct sched_entity *se)
 {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         unsigned long flags;
 
         /*
          * tasks cannot exit without having gone through wake_up_new_task() ->
          * post_init_entity_util_avg() which will have added things to the
          * cfs_rq, so we can remove unconditionally.
          *
          * Similarly for groups, they will have passed through
          * post_init_entity_util_avg() before unregister_sched_fair_group()
          * calls this.
          */
 
         sync_entity_load_avg(se);
 
         raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
         ++cfs_rq->removed.nr;
         cfs_rq->removed.util_avg        += se->avg.util_avg;
         cfs_rq->removed.load_avg        += se->avg.load_avg;
         cfs_rq->removed.runnable_sum    += se->avg.load_sum; /* == runnable_sum */
         raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
 }
 
 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
 {
         return cfs_rq->avg.runnable_load_avg;
 }
 
 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
 {
         return cfs_rq->avg.load_avg;
 }
 
 static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
 
 static inline unsigned long task_util(struct task_struct *p)
 {
         return READ_ONCE(p->se.avg.util_avg);
 }
 
 static inline unsigned long _task_util_est(struct task_struct *p)
 {
         struct util_est ue = READ_ONCE(p->se.avg.util_est);
 
         return max(ue.ewma, ue.enqueued);
 }
 
 static inline unsigned long task_util_est(struct task_struct *p)
 {
         return max(task_util(p), _task_util_est(p));
 }
 
 static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
                                     struct task_struct *p)
 {
         unsigned int enqueued;
 
         if (!sched_feat(UTIL_EST))
                 return;
 
         /* Update root cfs_rq's estimated utilization */
         enqueued  = cfs_rq->avg.util_est.enqueued;
         enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
         WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
 }
 
 /*
  * Check if a (signed) value is within a specified (unsigned) margin,
  * based on the observation that:
  *
  *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
  *
  * NOTE: this only works when value + maring < INT_MAX.
  */
 static inline bool within_margin(int value, int margin)
 {
         return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
 }
 
 static void
 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
 {
         long last_ewma_diff;
         struct util_est ue;
 
         if (!sched_feat(UTIL_EST))
                 return;
 
         /* Update root cfs_rq's estimated utilization */
         ue.enqueued  = cfs_rq->avg.util_est.enqueued;
         ue.enqueued -= min_t(unsigned int, ue.enqueued,
                              (_task_util_est(p) | UTIL_AVG_UNCHANGED));
         WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
 
         /*
          * Skip update of task's estimated utilization when the task has not
          * yet completed an activation, e.g. being migrated.
          */
         if (!task_sleep)
                 return;
 
         /*
          * If the PELT values haven't changed since enqueue time,
          * skip the util_est update.
          */
         ue = p->se.avg.util_est;
         if (ue.enqueued & UTIL_AVG_UNCHANGED)
                 return;
 
         /*
          * Skip update of task's estimated utilization when its EWMA is
          * already ~1% close to its last activation value.
          */
         ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
         last_ewma_diff = ue.enqueued - ue.ewma;
         if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
                 return;
 
         /*
          * Update Task's estimated utilization
          *
          * When *p completes an activation we can consolidate another sample
          * of the task size. This is done by storing the current PELT value
          * as ue.enqueued and by using this value to update the Exponential
          * Weighted Moving Average (EWMA):
          *
          *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
          *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
          *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
          *          = w * (      last_ewma_diff            ) +     ewma(t-1)
          *          = w * (last_ewma_diff  +  ewma(t-1) / w)
          *
          * Where 'w' is the weight of new samples, which is configured to be
          * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
          */
         ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
         ue.ewma  += last_ewma_diff;
         ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
         WRITE_ONCE(p->se.avg.util_est, ue);
 }
 
 #else /* CONFIG_SMP */
 
 static inline int
 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 {
         return 0;
 }
 
 #define UPDATE_TG       0x0
 #define SKIP_AGE_LOAD   0x0
 #define DO_ATTACH       0x0
 
 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
 {
         cfs_rq_util_change(cfs_rq, 0);
 }
 
 static inline void remove_entity_load_avg(struct sched_entity *se) {}
 
 static inline void
 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
 static inline void
 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
 
 static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
 {
         return 0;
 }
 
 static inline void
 util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
 
 static inline void
 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
                  bool task_sleep) {}
 
 #endif /* CONFIG_SMP */
 
 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 #ifdef CONFIG_SCHED_DEBUG
         s64 d = se->vruntime - cfs_rq->min_vruntime;
 
         if (d < 0)
                 d = -d;
 
         if (d > 3*sysctl_sched_latency)
                 schedstat_inc(cfs_rq->nr_spread_over);
 #endif
 }
 
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
         u64 vruntime = cfs_rq->min_vruntime;
 
         /*
          * The 'current' period is already promised to the current tasks,
          * however the extra weight of the new task will slow them down a
          * little, place the new task so that it fits in the slot that
          * stays open at the end.
          */
         if (initial && sched_feat(START_DEBIT))
                 vruntime += sched_vslice(cfs_rq, se);
 
         /* sleeps up to a single latency don't count. */
         if (!initial) {
                 unsigned long thresh = sysctl_sched_latency;
 
                 /*
                  * Halve their sleep time's effect, to allow
                  * for a gentler effect of sleepers:
                  */
                 if (sched_feat(GENTLE_FAIR_SLEEPERS))
                         thresh >>= 1;
 
                 vruntime -= thresh;
         }
 
         /* ensure we never gain time by being placed backwards. */
         se->vruntime = max_vruntime(se->vruntime, vruntime);
 }
 
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
 
 static inline void check_schedstat_required(void)
 {
 #ifdef CONFIG_SCHEDSTATS
         if (schedstat_enabled())
                 return;
 
         /* Force schedstat enabled if a dependent tracepoint is active */
         if (trace_sched_stat_wait_enabled()    ||
                         trace_sched_stat_sleep_enabled()   ||
                         trace_sched_stat_iowait_enabled()  ||
                         trace_sched_stat_blocked_enabled() ||
                         trace_sched_stat_runtime_enabled())  {
                 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
                              "stat_blocked and stat_runtime require the "
                              "kernel parameter schedstats=enable or "
                              "kernel.sched_schedstats=1\n");
         }
 #endif
 }
 
 
 /*
  * MIGRATION
  *
  *      dequeue
  *        update_curr()
  *          update_min_vruntime()
  *        vruntime -= min_vruntime
  *
  *      enqueue
  *        update_curr()
  *          update_min_vruntime()
  *        vruntime += min_vruntime
  *
  * this way the vruntime transition between RQs is done when both
  * min_vruntime are up-to-date.
  *
  * WAKEUP (remote)
  *
  *      ->migrate_task_rq_fair() (p->state == TASK_WAKING)
  *        vruntime -= min_vruntime
  *
  *      enqueue
  *        update_curr()
  *          update_min_vruntime()
  *        vruntime += min_vruntime
  *
  * this way we don't have the most up-to-date min_vruntime on the originating
  * CPU and an up-to-date min_vruntime on the destination CPU.
  */
 
 static void
 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
         bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
         bool curr = cfs_rq->curr == se;
 
         /*
          * If we're the current task, we must renormalise before calling
          * update_curr().
          */
         if (renorm && curr)
                 se->vruntime += cfs_rq->min_vruntime;
 
         update_curr(cfs_rq);
 
         /*
          * Otherwise, renormalise after, such that we're placed at the current
          * moment in time, instead of some random moment in the past. Being
          * placed in the past could significantly boost this task to the
          * fairness detriment of existing tasks.
          */
         if (renorm && !curr)
                 se->vruntime += cfs_rq->min_vruntime;
 
         /*
          * When enqueuing a sched_entity, we must:
          *   - Update loads to have both entity and cfs_rq synced with now.
          *   - Add its load to cfs_rq->runnable_avg
          *   - For group_entity, update its weight to reflect the new share of
          *     its group cfs_rq
          *   - Add its new weight to cfs_rq->load.weight
          */
         update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
         update_cfs_group(se);
         enqueue_runnable_load_avg(cfs_rq, se);
         account_entity_enqueue(cfs_rq, se);
 
         if (flags & ENQUEUE_WAKEUP)
                 place_entity(cfs_rq, se, 0);
 
         check_schedstat_required();
         update_stats_enqueue(cfs_rq, se, flags);
         check_spread(cfs_rq, se);
         if (!curr)
                 __enqueue_entity(cfs_rq, se);
         se->on_rq = 1;
 
         if (cfs_rq->nr_running == 1) {
                 list_add_leaf_cfs_rq(cfs_rq);
                 check_enqueue_throttle(cfs_rq);
         }
 }
 
 static void __clear_buddies_last(struct sched_entity *se)
 {
         for_each_sched_entity(se) {
                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
                 if (cfs_rq->last != se)
                         break;
 
                 cfs_rq->last = NULL;
         }
 }
 
 static void __clear_buddies_next(struct sched_entity *se)
 {
         for_each_sched_entity(se) {
                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
                 if (cfs_rq->next != se)
                         break;
 
                 cfs_rq->next = NULL;
         }
 }
 
 static void __clear_buddies_skip(struct sched_entity *se)
 {
         for_each_sched_entity(se) {
                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
                 if (cfs_rq->skip != se)
                         break;
 
                 cfs_rq->skip = NULL;
         }
 }
 
 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         if (cfs_rq->last == se)
                 __clear_buddies_last(se);
 
         if (cfs_rq->next == se)
                 __clear_buddies_next(se);
 
         if (cfs_rq->skip == se)
                 __clear_buddies_skip(se);
 }
 
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
 
 static void
 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
         /*
          * Update run-time statistics of the 'current'.
          */
         update_curr(cfs_rq);
 
         /*
          * When dequeuing a sched_entity, we must:
          *   - Update loads to have both entity and cfs_rq synced with now.
          *   - Substract its load from the cfs_rq->runnable_avg.
          *   - Substract its previous weight from cfs_rq->load.weight.
          *   - For group entity, update its weight to reflect the new share
          *     of its group cfs_rq.
          */
         update_load_avg(cfs_rq, se, UPDATE_TG);
         dequeue_runnable_load_avg(cfs_rq, se);
 
         update_stats_dequeue(cfs_rq, se, flags);
 
         clear_buddies(cfs_rq, se);
 
         if (se != cfs_rq->curr)
                 __dequeue_entity(cfs_rq, se);
         se->on_rq = 0;
         account_entity_dequeue(cfs_rq, se);
 
         /*
          * Normalize after update_curr(); which will also have moved
          * min_vruntime if @se is the one holding it back. But before doing
          * update_min_vruntime() again, which will discount @se's position and
          * can move min_vruntime forward still more.
          */
         if (!(flags & DEQUEUE_SLEEP))
                 se->vruntime -= cfs_rq->min_vruntime;
 
         /* return excess runtime on last dequeue */
         return_cfs_rq_runtime(cfs_rq);
 
         update_cfs_group(se);
 
         /*
          * Now advance min_vruntime if @se was the entity holding it back,
          * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
          * put back on, and if we advance min_vruntime, we'll be placed back
          * further than we started -- ie. we'll be penalized.
          */
         if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
                 update_min_vruntime(cfs_rq);
 }
 
 /*
  * Preempt the current task with a newly woken task if needed:
  */
 static void
 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
         unsigned long ideal_runtime, delta_exec;
         struct sched_entity *se;
         s64 delta;
 
         ideal_runtime = sched_slice(cfs_rq, curr);
         delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
         if (delta_exec > ideal_runtime) {
                 resched_curr(rq_of(cfs_rq));
                 /*
                  * The current task ran long enough, ensure it doesn't get
                  * re-elected due to buddy favours.
                  */
                 clear_buddies(cfs_rq, curr);
                 return;
         }
 
         /*
          * Ensure that a task that missed wakeup preemption by a
          * narrow margin doesn't have to wait for a full slice.
          * This also mitigates buddy induced latencies under load.
          */
         if (delta_exec < sysctl_sched_min_granularity)
                 return;
 
         se = __pick_first_entity(cfs_rq);
         delta = curr->vruntime - se->vruntime;
 
         if (delta < 0)
                 return;
 
         if (delta > ideal_runtime)
                 resched_curr(rq_of(cfs_rq));
 }
 
 static void
 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         /* 'current' is not kept within the tree. */
         if (se->on_rq) {
                 /*
                  * Any task has to be enqueued before it get to execute on
                  * a CPU. So account for the time it spent waiting on the
                  * runqueue.
                  */
                 update_stats_wait_end(cfs_rq, se);
                 __dequeue_entity(cfs_rq, se);
                 update_load_avg(cfs_rq, se, UPDATE_TG);
         }
 
         update_stats_curr_start(cfs_rq, se);
         cfs_rq->curr = se;
 
         /*
          * Track our maximum slice length, if the CPU's load is at
          * least twice that of our own weight (i.e. dont track it
          * when there are only lesser-weight tasks around):
          */
         if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
                 schedstat_set(se->statistics.slice_max,
                         max((u64)schedstat_val(se->statistics.slice_max),
                             se->sum_exec_runtime - se->prev_sum_exec_runtime));
         }
 
         se->prev_sum_exec_runtime = se->sum_exec_runtime;
 }
 
 static int
 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
 
 /*
  * Pick the next process, keeping these things in mind, in this order:
  * 1) keep things fair between processes/task groups
  * 2) pick the "next" process, since someone really wants that to run
  * 3) pick the "last" process, for cache locality
  * 4) do not run the "skip" process, if something else is available
  */
 static struct sched_entity *
 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
         struct sched_entity *left = __pick_first_entity(cfs_rq);
         struct sched_entity *se;
 
         /*
          * If curr is set we have to see if its left of the leftmost entity
          * still in the tree, provided there was anything in the tree at all.
          */
         if (!left || (curr && entity_before(curr, left)))
                 left = curr;
 
         se = left; /* ideally we run the leftmost entity */
 
         /*
          * Avoid running the skip buddy, if running something else can
          * be done without getting too unfair.
          */
         if (cfs_rq->skip == se) {
                 struct sched_entity *second;
 
                 if (se == curr) {
                         second = __pick_first_entity(cfs_rq);
                 } else {
                         second = __pick_next_entity(se);
                         if (!second || (curr && entity_before(curr, second)))
                                 second = curr;
                 }
 
                 if (second && wakeup_preempt_entity(second, left) < 1)
                         se = second;
         }
 
         /*
          * Prefer last buddy, try to return the CPU to a preempted task.
          */
         if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
                 se = cfs_rq->last;
 
         /*
          * Someone really wants this to run. If it's not unfair, run it.
          */
         if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
                 se = cfs_rq->next;
 
         clear_buddies(cfs_rq, se);
 
         return se;
 }
 
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
 
 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
 {
         /*
          * If still on the runqueue then deactivate_task()
          * was not called and update_curr() has to be done:
          */
         if (prev->on_rq)
                 update_curr(cfs_rq);
 
         /* throttle cfs_rqs exceeding runtime */
         check_cfs_rq_runtime(cfs_rq);
 
         check_spread(cfs_rq, prev);
 
         if (prev->on_rq) {
                 update_stats_wait_start(cfs_rq, prev);
                 /* Put 'current' back into the tree. */
                 __enqueue_entity(cfs_rq, prev);
                 /* in !on_rq case, update occurred at dequeue */
                 update_load_avg(cfs_rq, prev, 0);
         }
         cfs_rq->curr = NULL;
 }
 
 static void
 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 {
         /*
          * Update run-time statistics of the 'current'.
          */
         update_curr(cfs_rq);
 
         /*
          * Ensure that runnable average is periodically updated.
          */
         update_load_avg(cfs_rq, curr, UPDATE_TG);
         update_cfs_group(curr);
 
 #ifdef CONFIG_SCHED_HRTICK
         /*
          * queued ticks are scheduled to match the slice, so don't bother
          * validating it and just reschedule.
          */
         if (queued) {
                 resched_curr(rq_of(cfs_rq));
                 return;
         }
         /*
          * don't let the period tick interfere with the hrtick preemption
          */
         if (!sched_feat(DOUBLE_TICK) &&
                         hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
                 return;
 #endif
 
         if (cfs_rq->nr_running > 1)
                 check_preempt_tick(cfs_rq, curr);
 }
 
 
 /**************************************************
  * CFS bandwidth control machinery
  */
 
 #ifdef CONFIG_CFS_BANDWIDTH
 
 #ifdef HAVE_JUMP_LABEL
 static struct static_key __cfs_bandwidth_used;
 
 static inline bool cfs_bandwidth_used(void)
 {
         return static_key_false(&__cfs_bandwidth_used);
 }
 
 void cfs_bandwidth_usage_inc(void)
 {
         static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
 }
 
 void cfs_bandwidth_usage_dec(void)
 {
         static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
 }
 #else /* HAVE_JUMP_LABEL */
 static bool cfs_bandwidth_used(void)
 {
         return true;
 }
 
 void cfs_bandwidth_usage_inc(void) {}
 void cfs_bandwidth_usage_dec(void) {}
 #endif /* HAVE_JUMP_LABEL */
 
 /*
  * default period for cfs group bandwidth.
  * default: 0.1s, units: nanoseconds
  */
 static inline u64 default_cfs_period(void)
 {
         return 100000000ULL;
 }
 
 static inline u64 sched_cfs_bandwidth_slice(void)
 {
         return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
 }
 
 /*
  * Replenish runtime according to assigned quota and update expiration time.
  * We use sched_clock_cpu directly instead of rq->clock to avoid adding
  * additional synchronization around rq->lock.
  *
  * requires cfs_b->lock
  */
 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
 {
         u64 now;
 
         if (cfs_b->quota == RUNTIME_INF)
                 return;
 
         now = sched_clock_cpu(smp_processor_id());
         cfs_b->runtime = cfs_b->quota;
         cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
         cfs_b->expires_seq++;
 }
 
 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
 {
         return &tg->cfs_bandwidth;
 }
 
 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
 {
         if (unlikely(cfs_rq->throttle_count))
                 return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
 
         return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
 }
 
 /* returns 0 on failure to allocate runtime */
 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         struct task_group *tg = cfs_rq->tg;
         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
         u64 amount = 0, min_amount, expires;
         int expires_seq;
 
         /* note: this is a positive sum as runtime_remaining <= 0 */
         min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
 
         raw_spin_lock(&cfs_b->lock);
         if (cfs_b->quota == RUNTIME_INF)
                 amount = min_amount;
         else {
                 start_cfs_bandwidth(cfs_b);
 
                 if (cfs_b->runtime > 0) {
                         amount = min(cfs_b->runtime, min_amount);
                         cfs_b->runtime -= amount;
                         cfs_b->idle = 0;
                 }
         }
         expires_seq = cfs_b->expires_seq;
         expires = cfs_b->runtime_expires;
         raw_spin_unlock(&cfs_b->lock);
 
         cfs_rq->runtime_remaining += amount;
         /*
          * we may have advanced our local expiration to account for allowed
          * spread between our sched_clock and the one on which runtime was
          * issued.
          */
         if (cfs_rq->expires_seq != expires_seq) {
                 cfs_rq->expires_seq = expires_seq;
                 cfs_rq->runtime_expires = expires;
         }
 
         return cfs_rq->runtime_remaining > 0;
 }
 
 /*
  * Note: This depends on the synchronization provided by sched_clock and the
  * fact that rq->clock snapshots this value.
  */
 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
 
         /* if the deadline is ahead of our clock, nothing to do */
         if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
                 return;
 
         if (cfs_rq->runtime_remaining < 0)
                 return;
 
         /*
          * If the local deadline has passed we have to consider the
          * possibility that our sched_clock is 'fast' and the global deadline
          * has not truly expired.
          *
          * Fortunately we can check determine whether this the case by checking
          * whether the global deadline(cfs_b->expires_seq) has advanced.
          */
         if (cfs_rq->expires_seq == cfs_b->expires_seq) {
                 /* extend local deadline, drift is bounded above by 2 ticks */
                 cfs_rq->runtime_expires += TICK_NSEC;
         } else {
                 /* global deadline is ahead, expiration has passed */
                 cfs_rq->runtime_remaining = 0;
         }
 }
 
 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
 {
         /* dock delta_exec before expiring quota (as it could span periods) */
         cfs_rq->runtime_remaining -= delta_exec;
         expire_cfs_rq_runtime(cfs_rq);
 
         if (likely(cfs_rq->runtime_remaining > 0))
                 return;
 
         /*
          * if we're unable to extend our runtime we resched so that the active
          * hierarchy can be throttled
          */
         if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
                 resched_curr(rq_of(cfs_rq));
 }
 
 static __always_inline
 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
 {
         if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
                 return;
 
         __account_cfs_rq_runtime(cfs_rq, delta_exec);
 }
 
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
 {
         return cfs_bandwidth_used() && cfs_rq->throttled;
 }
 
 /* check whether cfs_rq, or any parent, is throttled */
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
 {
         return cfs_bandwidth_used() && cfs_rq->throttle_count;
 }
 
 /*
  * Ensure that neither of the group entities corresponding to src_cpu or
  * dest_cpu are members of a throttled hierarchy when performing group
  * load-balance operations.
  */
 static inline int throttled_lb_pair(struct task_group *tg,
                                     int src_cpu, int dest_cpu)
 {
         struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
 
         src_cfs_rq = tg->cfs_rq[src_cpu];
         dest_cfs_rq = tg->cfs_rq[dest_cpu];
 
         return throttled_hierarchy(src_cfs_rq) ||
                throttled_hierarchy(dest_cfs_rq);
 }
 
 /* updated child weight may affect parent so we have to do this bottom up */
 static int tg_unthrottle_up(struct task_group *tg, void *data)
 {
         struct rq *rq = data;
         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
         cfs_rq->throttle_count--;
         if (!cfs_rq->throttle_count) {
                 /* adjust cfs_rq_clock_task() */
                 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
                                              cfs_rq->throttled_clock_task;
         }
 
         return 0;
 }
 
 static int tg_throttle_down(struct task_group *tg, void *data)
 {
         struct rq *rq = data;
         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
         /* group is entering throttled state, stop time */
         if (!cfs_rq->throttle_count)
                 cfs_rq->throttled_clock_task = rq_clock_task(rq);
         cfs_rq->throttle_count++;
 
         return 0;
 }
 
 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 {
         struct rq *rq = rq_of(cfs_rq);
         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
         struct sched_entity *se;
         long task_delta, dequeue = 1;
         bool empty;
 
         se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
 
         /* freeze hierarchy runnable averages while throttled */
         rcu_read_lock();
         walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
         rcu_read_unlock();
 
         task_delta = cfs_rq->h_nr_running;
         for_each_sched_entity(se) {
                 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
                 /* throttled entity or throttle-on-deactivate */
                 if (!se->on_rq)
                         break;
 
                 if (dequeue)
                         dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
                 qcfs_rq->h_nr_running -= task_delta;
 
                 if (qcfs_rq->load.weight)
                         dequeue = 0;
         }
 
         if (!se)
                 sub_nr_running(rq, task_delta);
 
         cfs_rq->throttled = 1;
         cfs_rq->throttled_clock = rq_clock(rq);
         raw_spin_lock(&cfs_b->lock);
         empty = list_empty(&cfs_b->throttled_cfs_rq);
 
         /*
          * Add to the _head_ of the list, so that an already-started
          * distribute_cfs_runtime will not see us
          */
         list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
 
         /*
          * If we're the first throttled task, make sure the bandwidth
          * timer is running.
          */
         if (empty)
                 start_cfs_bandwidth(cfs_b);
 
         raw_spin_unlock(&cfs_b->lock);
 }
 
 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 {
         struct rq *rq = rq_of(cfs_rq);
         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
         struct sched_entity *se;
         int enqueue = 1;
         long task_delta;
 
         se = cfs_rq->tg->se[cpu_of(rq)];
 
         cfs_rq->throttled = 0;
 
         update_rq_clock(rq);
 
         raw_spin_lock(&cfs_b->lock);
         cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
         list_del_rcu(&cfs_rq->throttled_list);
         raw_spin_unlock(&cfs_b->lock);
 
         /* update hierarchical throttle state */
         walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
 
         if (!cfs_rq->load.weight)
                 return;
 
         task_delta = cfs_rq->h_nr_running;
         for_each_sched_entity(se) {
                 if (se->on_rq)
                         enqueue = 0;
 
                 cfs_rq = cfs_rq_of(se);
                 if (enqueue)
                         enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
                 cfs_rq->h_nr_running += task_delta;
 
                 if (cfs_rq_throttled(cfs_rq))
                         break;
         }
 
         if (!se)
                 add_nr_running(rq, task_delta);
 
         /* Determine whether we need to wake up potentially idle CPU: */
         if (rq->curr == rq->idle && rq->cfs.nr_running)
                 resched_curr(rq);
 }
 
 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
                 u64 remaining, u64 expires)
 {
         struct cfs_rq *cfs_rq;
         u64 runtime;
         u64 starting_runtime = remaining;
 
         rcu_read_lock();
         list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
                                 throttled_list) {
                 struct rq *rq = rq_of(cfs_rq);
                 struct rq_flags rf;
 
                 rq_lock(rq, &rf);
                 if (!cfs_rq_throttled(cfs_rq))
                         goto next;
 
                 runtime = -cfs_rq->runtime_remaining + 1;
                 if (runtime > remaining)
                         runtime = remaining;
                 remaining -= runtime;
 
                 cfs_rq->runtime_remaining += runtime;
                 cfs_rq->runtime_expires = expires;
 
                 /* we check whether we're throttled above */
                 if (cfs_rq->runtime_remaining > 0)
                         unthrottle_cfs_rq(cfs_rq);
 
 next:
                 rq_unlock(rq, &rf);
 
                 if (!remaining)
                         break;
         }
         rcu_read_unlock();
 
         return starting_runtime - remaining;
 }
 
 /*
  * Responsible for refilling a task_group's bandwidth and unthrottling its
  * cfs_rqs as appropriate. If there has been no activity within the last
  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
  * used to track this state.
  */
 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
 {
         u64 runtime, runtime_expires;
         int throttled;
 
         /* no need to continue the timer with no bandwidth constraint */
         if (cfs_b->quota == RUNTIME_INF)
                 goto out_deactivate;
 
         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
         cfs_b->nr_periods += overrun;
 
         /*
          * idle depends on !throttled (for the case of a large deficit), and if
          * we're going inactive then everything else can be deferred
          */
         if (cfs_b->idle && !throttled)
                 goto out_deactivate;
 
         __refill_cfs_bandwidth_runtime(cfs_b);
 
         if (!throttled) {
                 /* mark as potentially idle for the upcoming period */
                 cfs_b->idle = 1;
                 return 0;
         }
 
         /* account preceding periods in which throttling occurred */
         cfs_b->nr_throttled += overrun;
 
         runtime_expires = cfs_b->runtime_expires;
 
         /*
          * This check is repeated as we are holding onto the new bandwidth while
          * we unthrottle. This can potentially race with an unthrottled group
          * trying to acquire new bandwidth from the global pool. This can result
          * in us over-using our runtime if it is all used during this loop, but
          * only by limited amounts in that extreme case.
          */
         while (throttled && cfs_b->runtime > 0) {
                 runtime = cfs_b->runtime;
                 raw_spin_unlock(&cfs_b->lock);
                 /* we can't nest cfs_b->lock while distributing bandwidth */
                 runtime = distribute_cfs_runtime(cfs_b, runtime,
                                                  runtime_expires);
                 raw_spin_lock(&cfs_b->lock);
 
                 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
 
                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
         }
 
         /*
          * While we are ensured activity in the period following an
          * unthrottle, this also covers the case in which the new bandwidth is
          * insufficient to cover the existing bandwidth deficit.  (Forcing the
          * timer to remain active while there are any throttled entities.)
          */
         cfs_b->idle = 0;
 
         return 0;
 
 out_deactivate:
         return 1;
 }
 
 /* a cfs_rq won't donate quota below this amount */
 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
 /* minimum remaining period time to redistribute slack quota */
 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
 /* how long we wait to gather additional slack before distributing */
 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
 
 /*
  * Are we near the end of the current quota period?
  *
  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
  * hrtimer base being cleared by hrtimer_start. In the case of
  * migrate_hrtimers, base is never cleared, so we are fine.
  */
 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 {
         struct hrtimer *refresh_timer = &cfs_b->period_timer;
         u64 remaining;
 
         /* if the call-back is running a quota refresh is already occurring */
         if (hrtimer_callback_running(refresh_timer))
                 return 1;
 
         /* is a quota refresh about to occur? */
         remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
         if (remaining < min_expire)
                 return 1;
 
         return 0;
 }
 
 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
 {
         u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
 
         /* if there's a quota refresh soon don't bother with slack */
         if (runtime_refresh_within(cfs_b, min_left))
                 return;
 
         hrtimer_start(&cfs_b->slack_timer,
                         ns_to_ktime(cfs_bandwidth_slack_period),
                         HRTIMER_MODE_REL);
 }
 
 /* we know any runtime found here is valid as update_curr() precedes return */
 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
         s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
 
         if (slack_runtime <= 0)
                 return;
 
         raw_spin_lock(&cfs_b->lock);
         if (cfs_b->quota != RUNTIME_INF &&
             cfs_rq->runtime_expires == cfs_b->runtime_expires) {
                 cfs_b->runtime += slack_runtime;
 
                 /* we are under rq->lock, defer unthrottling using a timer */
                 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
                     !list_empty(&cfs_b->throttled_cfs_rq))
                         start_cfs_slack_bandwidth(cfs_b);
         }
         raw_spin_unlock(&cfs_b->lock);
 
         /* even if it's not valid for return we don't want to try again */
         cfs_rq->runtime_remaining -= slack_runtime;
 }
 
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         if (!cfs_bandwidth_used())
                 return;
 
         if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
                 return;
 
         __return_cfs_rq_runtime(cfs_rq);
 }
 
 /*
  * This is done with a timer (instead of inline with bandwidth return) since
  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
  */
 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
 {
         u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
         u64 expires;
 
         /* confirm we're still not at a refresh boundary */
         raw_spin_lock(&cfs_b->lock);
         if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
                 raw_spin_unlock(&cfs_b->lock);
                 return;
         }
 
         if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
                 runtime = cfs_b->runtime;
 
         expires = cfs_b->runtime_expires;
         raw_spin_unlock(&cfs_b->lock);
 
         if (!runtime)
                 return;
 
         runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
 
         raw_spin_lock(&cfs_b->lock);
         if (expires == cfs_b->runtime_expires)
                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
         raw_spin_unlock(&cfs_b->lock);
 }
 
 /*
  * When a group wakes up we want to make sure that its quota is not already
  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
  * runtime as update_curr() throttling can not not trigger until it's on-rq.
  */
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
 {
         if (!cfs_bandwidth_used())
                 return;
 
         /* an active group must be handled by the update_curr()->put() path */
         if (!cfs_rq->runtime_enabled || cfs_rq->curr)
                 return;
 
         /* ensure the group is not already throttled */
         if (cfs_rq_throttled(cfs_rq))
                 return;
 
         /* update runtime allocation */
         account_cfs_rq_runtime(cfs_rq, 0);
         if (cfs_rq->runtime_remaining <= 0)
                 throttle_cfs_rq(cfs_rq);
 }
 
 static void sync_throttle(struct task_group *tg, int cpu)
 {
         struct cfs_rq *pcfs_rq, *cfs_rq;
 
         if (!cfs_bandwidth_used())
                 return;
 
         if (!tg->parent)
                 return;
 
         cfs_rq = tg->cfs_rq[cpu];
         pcfs_rq = tg->parent->cfs_rq[cpu];
 
         cfs_rq->throttle_count = pcfs_rq->throttle_count;
         cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
 }
 
 /* conditionally throttle active cfs_rq's from put_prev_entity() */
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         if (!cfs_bandwidth_used())
                 return false;
 
         if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
                 return false;
 
         /*
          * it's possible for a throttled entity to be forced into a running
          * state (e.g. set_curr_task), in this case we're finished.
          */
         if (cfs_rq_throttled(cfs_rq))
                 return true;
 
         throttle_cfs_rq(cfs_rq);
         return true;
 }
 
 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
 {
         struct cfs_bandwidth *cfs_b =
                 container_of(timer, struct cfs_bandwidth, slack_timer);
 
         do_sched_cfs_slack_timer(cfs_b);
 
         return HRTIMER_NORESTART;
 }
 
 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
 {
         struct cfs_bandwidth *cfs_b =
                 container_of(timer, struct cfs_bandwidth, period_timer);
         int overrun;
         int idle = 0;
 
         raw_spin_lock(&cfs_b->lock);
         for (;;) {
                 overrun = hrtimer_forward_now(timer, cfs_b->period);
                 if (!overrun)
                         break;
 
                 idle = do_sched_cfs_period_timer(cfs_b, overrun);
         }
         if (idle)
                 cfs_b->period_active = 0;
         raw_spin_unlock(&cfs_b->lock);
 
         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
 }
 
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
         raw_spin_lock_init(&cfs_b->lock);
         cfs_b->runtime = 0;
         cfs_b->quota = RUNTIME_INF;
         cfs_b->period = ns_to_ktime(default_cfs_period());
 
         INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
         hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
         cfs_b->period_timer.function = sched_cfs_period_timer;
         hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         cfs_b->slack_timer.function = sched_cfs_slack_timer;
 }
 
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
         cfs_rq->runtime_enabled = 0;
         INIT_LIST_HEAD(&cfs_rq->throttled_list);
 }
 
 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
         lockdep_assert_held(&cfs_b->lock);
 
         if (!cfs_b->period_active) {
                 cfs_b->period_active = 1;
                 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
                 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
         }
 }
 
 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
         /* init_cfs_bandwidth() was not called */
         if (!cfs_b->throttled_cfs_rq.next)
                 return;
 
         hrtimer_cancel(&cfs_b->period_timer);
         hrtimer_cancel(&cfs_b->slack_timer);
 }
 
 /*
  * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
  *
  * The race is harmless, since modifying bandwidth settings of unhooked group
  * bits doesn't do much.
  */
 
 /* cpu online calback */
 static void __maybe_unused update_runtime_enabled(struct rq *rq)
 {
         struct task_group *tg;
 
         lockdep_assert_held(&rq->lock);
 
         rcu_read_lock();
         list_for_each_entry_rcu(tg, &task_groups, list) {
                 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
                 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
                 raw_spin_lock(&cfs_b->lock);
                 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
                 raw_spin_unlock(&cfs_b->lock);
         }
         rcu_read_unlock();
 }
 
 /* cpu offline callback */
 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
 {
         struct task_group *tg;
 
         lockdep_assert_held(&rq->lock);
 
         rcu_read_lock();
         list_for_each_entry_rcu(tg, &task_groups, list) {
                 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
                 if (!cfs_rq->runtime_enabled)
                         continue;
 
                 /*
                  * clock_task is not advancing so we just need to make sure
                  * there's some valid quota amount
                  */
                 cfs_rq->runtime_remaining = 1;
                 /*
                  * Offline rq is schedulable till CPU is completely disabled
                  * in take_cpu_down(), so we prevent new cfs throttling here.
                  */
                 cfs_rq->runtime_enabled = 0;
 
                 if (cfs_rq_throttled(cfs_rq))
                         unthrottle_cfs_rq(cfs_rq);
         }
         rcu_read_unlock();
 }
 
 #else /* CONFIG_CFS_BANDWIDTH */
 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
 {
         return rq_clock_task(rq_of(cfs_rq));
 }
 
 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
 static inline void sync_throttle(struct task_group *tg, int cpu) {}
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
 
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
 {
         return 0;
 }
 
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
 {
         return 0;
 }
 
 static inline int throttled_lb_pair(struct task_group *tg,
                                     int src_cpu, int dest_cpu)
 {
         return 0;
 }
 
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
 #endif
 
 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
 {
         return NULL;
 }
 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
 static inline void update_runtime_enabled(struct rq *rq) {}
 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
 
 #endif /* CONFIG_CFS_BANDWIDTH */
 
 /**************************************************
  * CFS operations on tasks:
  */
 
 #ifdef CONFIG_SCHED_HRTICK
 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
 {
         struct sched_entity *se = &p->se;
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
         SCHED_WARN_ON(task_rq(p) != rq);
 
         if (rq->cfs.h_nr_running > 1) {
                 u64 slice = sched_slice(cfs_rq, se);
                 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
                 s64 delta = slice - ran;
 
                 if (delta < 0) {
                         if (rq->curr == p)
                                 resched_curr(rq);
                         return;
                 }
                 hrtick_start(rq, delta);
         }
 }
 
 /*
  * called from enqueue/dequeue and updates the hrtick when the
  * current task is from our class and nr_running is low enough
  * to matter.
  */
 static void hrtick_update(struct rq *rq)
 {
         struct task_struct *curr = rq->curr;
 
         if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
                 return;
 
         if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
                 hrtick_start_fair(rq, curr);
 }
 #else /* !CONFIG_SCHED_HRTICK */
 static inline void
 hrtick_start_fair(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline void hrtick_update(struct rq *rq)
 {
 }
 #endif
 
 /*
  * The enqueue_task method is called before nr_running is
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
 static void
 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
         struct cfs_rq *cfs_rq;
         struct sched_entity *se = &p->se;
 
         /*
          * If in_iowait is set, the code below may not trigger any cpufreq
          * utilization updates, so do it here explicitly with the IOWAIT flag
          * passed.
          */
         if (p->in_iowait)
                 cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
 
         for_each_sched_entity(se) {
                 if (se->on_rq)
                         break;
                 cfs_rq = cfs_rq_of(se);
                 enqueue_entity(cfs_rq, se, flags);
 
                 /*
                  * end evaluation on encountering a throttled cfs_rq
                  *
                  * note: in the case of encountering a throttled cfs_rq we will
                  * post the final h_nr_running increment below.
                  */
                 if (cfs_rq_throttled(cfs_rq))
                         break;
                 cfs_rq->h_nr_running++;
 
                 flags = ENQUEUE_WAKEUP;
         }
 
         for_each_sched_entity(se) {
                 cfs_rq = cfs_rq_of(se);
                 cfs_rq->h_nr_running++;
 
                 if (cfs_rq_throttled(cfs_rq))
                         break;
 
                 update_load_avg(cfs_rq, se, UPDATE_TG);
                 update_cfs_group(se);
         }
 
         if (!se)
                 add_nr_running(rq, 1);
 
         util_est_enqueue(&rq->cfs, p);
         hrtick_update(rq);
 }
 
 static void set_next_buddy(struct sched_entity *se);
 
 /*
  * The dequeue_task method is called before nr_running is
  * decreased. We remove the task from the rbtree and
  * update the fair scheduling stats:
  */
 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
         struct cfs_rq *cfs_rq;
         struct sched_entity *se = &p->se;
         int task_sleep = flags & DEQUEUE_SLEEP;
 
         for_each_sched_entity(se) {
                 cfs_rq = cfs_rq_of(se);
                 dequeue_entity(cfs_rq, se, flags);
 
                 /*
                  * end evaluation on encountering a throttled cfs_rq
                  *
                  * note: in the case of encountering a throttled cfs_rq we will
                  * post the final h_nr_running decrement below.
                 */
                 if (cfs_rq_throttled(cfs_rq))
                         break;
                 cfs_rq->h_nr_running--;
 
                 /* Don't dequeue parent if it has other entities besides us */
                 if (cfs_rq->load.weight) {
                         /* Avoid re-evaluating load for this entity: */
                         se = parent_entity(se);
                         /*
                          * Bias pick_next to pick a task from this cfs_rq, as
                          * p is sleeping when it is within its sched_slice.
                          */
                         if (task_sleep && se && !throttled_hierarchy(cfs_rq))
                                 set_next_buddy(se);
                         break;
                 }
                 flags |= DEQUEUE_SLEEP;
         }
 
         for_each_sched_entity(se) {
                 cfs_rq = cfs_rq_of(se);
                 cfs_rq->h_nr_running--;
 
                 if (cfs_rq_throttled(cfs_rq))
                         break;
 
                 update_load_avg(cfs_rq, se, UPDATE_TG);
                 update_cfs_group(se);
         }
 
         if (!se)
                 sub_nr_running(rq, 1);
 
         util_est_dequeue(&rq->cfs, p, task_sleep);
         hrtick_update(rq);
 }
 
 #ifdef CONFIG_SMP
 
 /* Working cpumask for: load_balance, load_balance_newidle. */
 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
 DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
 
 #ifdef CONFIG_NO_HZ_COMMON
 /*
  * per rq 'load' arrray crap; XXX kill this.
  */
 
 /*
  * The exact cpuload calculated at every tick would be:
  *
  *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
  *
  * If a CPU misses updates for n ticks (as it was idle) and update gets
  * called on the n+1-th tick when CPU may be busy, then we have:
  *
  *   load_n   = (1 - 1/2^i)^n * load_0
  *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
  *
  * decay_load_missed() below does efficient calculation of
  *
  *   load' = (1 - 1/2^i)^n * load
  *
  * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
  * This allows us to precompute the above in said factors, thereby allowing the
  * reduction of an arbitrary n in O(log_2 n) steps. (See also
  * fixed_power_int())
  *
  * The calculation is approximated on a 128 point scale.
  */
 #define DEGRADE_SHIFT           7
 
 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
         {   0,   0,  0,  0,  0,  0, 0, 0 },
         {  64,  32,  8,  0,  0,  0, 0, 0 },
         {  96,  72, 40, 12,  1,  0, 0, 0 },
         { 112,  98, 75, 43, 15,  1, 0, 0 },
         { 120, 112, 98, 76, 45, 16, 2, 0 }
 };
 
 /*
  * Update cpu_load for any missed ticks, due to tickless idle. The backlog
  * would be when CPU is idle and so we just decay the old load without
  * adding any new load.
  */
 static unsigned long
 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
 {
         int j = 0;
 
         if (!missed_updates)
                 return load;
 
         if (missed_updates >= degrade_zero_ticks[idx])
                 return 0;
 
         if (idx == 1)
                 return load >> missed_updates;
 
         while (missed_updates) {
                 if (missed_updates % 2)
                         load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
 
                 missed_updates >>= 1;
                 j++;
         }
         return load;
 }
 
 static struct {
         cpumask_var_t idle_cpus_mask;
         atomic_t nr_cpus;
         int has_blocked;                /* Idle CPUS has blocked load */
         unsigned long next_balance;     /* in jiffy units */
         unsigned long next_blocked;     /* Next update of blocked load in jiffies */
 } nohz ____cacheline_aligned;
 
 #endif /* CONFIG_NO_HZ_COMMON */
 
 /**
  * __cpu_load_update - update the rq->cpu_load[] statistics
  * @this_rq: The rq to update statistics for
  * @this_load: The current load
  * @pending_updates: The number of missed updates
  *
  * Update rq->cpu_load[] statistics. This function is usually called every
  * scheduler tick (TICK_NSEC).
  *
  * This function computes a decaying average:
  *
  *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
  *
  * Because of NOHZ it might not get called on every tick which gives need for
  * the @pending_updates argument.
  *
  *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
  *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
  *             = A * (A * load[i]_n-2 + B) + B
  *             = A * (A * (A * load[i]_n-3 + B) + B) + B
  *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
  *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
  *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
  *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
  *
  * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
  * any change in load would have resulted in the tick being turned back on.
  *
  * For regular NOHZ, this reduces to:
  *
  *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
  *
  * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
  * term.
  */
 static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
                             unsigned long pending_updates)
 {
         unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
         int i, scale;
 
         this_rq->nr_load_updates++;
 
         /* Update our load: */
         this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
         for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
                 unsigned long old_load, new_load;
 
                 /* scale is effectively 1 << i now, and >> i divides by scale */
 
                 old_load = this_rq->cpu_load[i];
 #ifdef CONFIG_NO_HZ_COMMON
                 old_load = decay_load_missed(old_load, pending_updates - 1, i);
                 if (tickless_load) {
                         old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
                         /*
                          * old_load can never be a negative value because a
                          * decayed tickless_load cannot be greater than the
                          * original tickless_load.
                          */
                         old_load += tickless_load;
                 }
 #endif
                 new_load = this_load;
                 /*
                  * Round up the averaging division if load is increasing. This
                  * prevents us from getting stuck on 9 if the load is 10, for
                  * example.
                  */
                 if (new_load > old_load)
                         new_load += scale - 1;
 
                 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
         }
 
         sched_avg_update(this_rq);
 }
 
 /* Used instead of source_load when we know the type == 0 */
 static unsigned long weighted_cpuload(struct rq *rq)
 {
         return cfs_rq_runnable_load_avg(&rq->cfs);
 }
 
 #ifdef CONFIG_NO_HZ_COMMON
 /*
  * There is no sane way to deal with nohz on smp when using jiffies because the
  * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
  * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
  *
  * Therefore we need to avoid the delta approach from the regular tick when
  * possible since that would seriously skew the load calculation. This is why we
  * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
  * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
  * loop exit, nohz_idle_balance, nohz full exit...)
  *
  * This means we might still be one tick off for nohz periods.
  */
 
 static void cpu_load_update_nohz(struct rq *this_rq,
                                  unsigned long curr_jiffies,
                                  unsigned long load)
 {
         unsigned long pending_updates;
 
         pending_updates = curr_jiffies - this_rq->last_load_update_tick;
         if (pending_updates) {
                 this_rq->last_load_update_tick = curr_jiffies;
                 /*
                  * In the regular NOHZ case, we were idle, this means load 0.
                  * In the NOHZ_FULL case, we were non-idle, we should consider
                  * its weighted load.
                  */
                 cpu_load_update(this_rq, load, pending_updates);
         }
 }
 
 /*
  * Called from nohz_idle_balance() to update the load ratings before doing the
  * idle balance.
  */
 static void cpu_load_update_idle(struct rq *this_rq)
 {
         /*
          * bail if there's load or we're actually up-to-date.
          */
         if (weighted_cpuload(this_rq))
                 return;
 
         cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
 }
 
 /*
  * Record CPU load on nohz entry so we know the tickless load to account
  * on nohz exit. cpu_load[0] happens then to be updated more frequently
  * than other cpu_load[idx] but it should be fine as cpu_load readers
  * shouldn't rely into synchronized cpu_load[*] updates.
  */
 void cpu_load_update_nohz_start(void)
 {
         struct rq *this_rq = this_rq();
 
         /*
          * This is all lockless but should be fine. If weighted_cpuload changes
          * concurrently we'll exit nohz. And cpu_load write can race with
          * cpu_load_update_idle() but both updater would be writing the same.
          */
         this_rq->cpu_load[0] = weighted_cpuload(this_rq);
 }
 
 /*
  * Account the tickless load in the end of a nohz frame.
  */
 void cpu_load_update_nohz_stop(void)
 {
         unsigned long curr_jiffies = READ_ONCE(jiffies);
         struct rq *this_rq = this_rq();
         unsigned long load;
         struct rq_flags rf;
 
         if (curr_jiffies == this_rq->last_load_update_tick)
                 return;
 
         load = weighted_cpuload(this_rq);
         rq_lock(this_rq, &rf);
         update_rq_clock(this_rq);
         cpu_load_update_nohz(this_rq, curr_jiffies, load);
         rq_unlock(this_rq, &rf);
 }
 #else /* !CONFIG_NO_HZ_COMMON */
 static inline void cpu_load_update_nohz(struct rq *this_rq,
                                         unsigned long curr_jiffies,
                                         unsigned long load) { }
 #endif /* CONFIG_NO_HZ_COMMON */
 
 static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
 {
 #ifdef CONFIG_NO_HZ_COMMON
         /* See the mess around cpu_load_update_nohz(). */
         this_rq->last_load_update_tick = READ_ONCE(jiffies);
 #endif
         cpu_load_update(this_rq, load, 1);
 }
 
 /*
  * Called from scheduler_tick()
  */
 void cpu_load_update_active(struct rq *this_rq)
 {
         unsigned long load = weighted_cpuload(this_rq);
 
         if (tick_nohz_tick_stopped())
                 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
         else
                 cpu_load_update_periodic(this_rq, load);
 }
 
 /*
  * Return a low guess at the load of a migration-source CPU weighted
  * according to the scheduling class and "nice" value.
  *
  * We want to under-estimate the load of migration sources, to
  * balance conservatively.
  */
 static unsigned long source_load(int cpu, int type)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long total = weighted_cpuload(rq);
 
         if (type == 0 || !sched_feat(LB_BIAS))
                 return total;
 
         return min(rq->cpu_load[type-1], total);
 }
 
 /*
  * Return a high guess at the load of a migration-target CPU weighted
  * according to the scheduling class and "nice" value.
  */
 static unsigned long target_load(int cpu, int type)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long total = weighted_cpuload(rq);
 
         if (type == 0 || !sched_feat(LB_BIAS))
                 return total;
 
         return max(rq->cpu_load[type-1], total);
 }
 
 static unsigned long capacity_of(int cpu)
 {
         return cpu_rq(cpu)->cpu_capacity;
 }
 
 static unsigned long capacity_orig_of(int cpu)
 {
         return cpu_rq(cpu)->cpu_capacity_orig;
 }
 
 static unsigned long cpu_avg_load_per_task(int cpu)
 {
         struct rq *rq = cpu_rq(cpu);
         unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
         unsigned long load_avg = weighted_cpuload(rq);
 
         if (nr_running)
                 return load_avg / nr_running;
 
         return 0;
 }
 
 static void record_wakee(struct task_struct *p)
 {
         /*
          * Only decay a single time; tasks that have less then 1 wakeup per
          * jiffy will not have built up many flips.
          */
         if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
                 current->wakee_flips >>= 1;
                 current->wakee_flip_decay_ts = jiffies;
         }
 
         if (current->last_wakee != p) {
                 current->last_wakee = p;
                 current->wakee_flips++;
         }
 }
 
 /*
  * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
  *
  * A waker of many should wake a different task than the one last awakened
  * at a frequency roughly N times higher than one of its wakees.
  *
  * In order to determine whether we should let the load spread vs consolidating
  * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
  * partner, and a factor of lls_size higher frequency in the other.
  *
  * With both conditions met, we can be relatively sure that the relationship is
  * non-monogamous, with partner count exceeding socket size.
  *
  * Waker/wakee being client/server, worker/dispatcher, interrupt source or
  * whatever is irrelevant, spread criteria is apparent partner count exceeds
  * socket size.
  */
 static int wake_wide(struct task_struct *p)
 {
         unsigned int master = current->wakee_flips;
         unsigned int slave = p->wakee_flips;
         int factor = this_cpu_read(sd_llc_size);
 
         if (master < slave)
                 swap(master, slave);
         if (slave < factor || master < slave * factor)
                 return 0;
         return 1;
 }
 
 /*
  * The purpose of wake_affine() is to quickly determine on which CPU we can run
  * soonest. For the purpose of speed we only consider the waking and previous
  * CPU.
  *
  * wake_affine_idle() - only considers 'now', it check if the waking CPU is
  *                      cache-affine and is (or will be) idle.
  *
  * wake_affine_weight() - considers the weight to reflect the average
  *                        scheduling latency of the CPUs. This seems to work
  *                        for the overloaded case.
  */
 static int
 wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 {
         /*
          * If this_cpu is idle, it implies the wakeup is from interrupt
          * context. Only allow the move if cache is shared. Otherwise an
          * interrupt intensive workload could force all tasks onto one
          * node depending on the IO topology or IRQ affinity settings.
          *
          * If the prev_cpu is idle and cache affine then avoid a migration.
          * There is no guarantee that the cache hot data from an interrupt
          * is more important than cache hot data on the prev_cpu and from
          * a cpufreq perspective, it's better to have higher utilisation
          * on one CPU.
          */
         if (idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
                 return idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
 
         if (sync && cpu_rq(this_cpu)->nr_running == 1)
                 return this_cpu;
 
         return nr_cpumask_bits;
 }
 
 static int
 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
                    int this_cpu, int prev_cpu, int sync)
 {
         s64 this_eff_load, prev_eff_load;
         unsigned long task_load;
 
         this_eff_load = target_load(this_cpu, sd->wake_idx);
 
         if (sync) {
                 unsigned long current_load = task_h_load(current);
 
                 if (current_load > this_eff_load)
                         return this_cpu;
 
                 this_eff_load -= current_load;
         }
 
         task_load = task_h_load(p);
 
         this_eff_load += task_load;
         if (sched_feat(WA_BIAS))
                 this_eff_load *= 100;
         this_eff_load *= capacity_of(prev_cpu);
 
         prev_eff_load = source_load(prev_cpu, sd->wake_idx);
         prev_eff_load -= task_load;
         if (sched_feat(WA_BIAS))
                 prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
         prev_eff_load *= capacity_of(this_cpu);
 
         /*
          * If sync, adjust the weight of prev_eff_load such that if
          * prev_eff == this_eff that select_idle_sibling() will consider
          * stacking the wakee on top of the waker if no other CPU is
          * idle.
          */
         if (sync)
                 prev_eff_load += 1;
 
         return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
 }
 
 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
                        int this_cpu, int prev_cpu, int sync)
 {
         int target = nr_cpumask_bits;
 
         if (sched_feat(WA_IDLE))
                 target = wake_affine_idle(this_cpu, prev_cpu, sync);
 
         if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
                 target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
 
         schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
         if (target == nr_cpumask_bits)
                 return prev_cpu;
 
         schedstat_inc(sd->ttwu_move_affine);
         schedstat_inc(p->se.statistics.nr_wakeups_affine);
         return target;
 }
 
 static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
 
 static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
 {
         return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0);
 }
 
 /*
  * find_idlest_group finds and returns the least busy CPU group within the
  * domain.
  *
  * Assumes p is allowed on at least one CPU in sd.
  */
 static struct sched_group *
 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
                   int this_cpu, int sd_flag)
 {
         struct sched_group *idlest = NULL, *group = sd->groups;
         struct sched_group *most_spare_sg = NULL;
         unsigned long min_runnable_load = ULONG_MAX;
         unsigned long this_runnable_load = ULONG_MAX;
         unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
         unsigned long most_spare = 0, this_spare = 0;
         int load_idx = sd->forkexec_idx;
         int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
         unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
                                 (sd->imbalance_pct-100) / 100;
 
         if (sd_flag & SD_BALANCE_WAKE)
                 load_idx = sd->wake_idx;
 
         do {
                 unsigned long load, avg_load, runnable_load;
                 unsigned long spare_cap, max_spare_cap;
                 int local_group;
                 int i;
 
                 /* Skip over this group if it has no CPUs allowed */
                 if (!cpumask_intersects(sched_group_span(group),
                                         &p->cpus_allowed))
                         continue;
 
                 local_group = cpumask_test_cpu(this_cpu,
                                                sched_group_span(group));
 
                 /*
                  * Tally up the load of all CPUs in the group and find
                  * the group containing the CPU with most spare capacity.
                  */
                 avg_load = 0;
                 runnable_load = 0;
                 max_spare_cap = 0;
 
                 for_each_cpu(i, sched_group_span(group)) {
                         /* Bias balancing toward CPUs of our domain */
                         if (local_group)
                                 load = source_load(i, load_idx);
                         else
                                 load = target_load(i, load_idx);
 
                         runnable_load += load;
 
                         avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
 
                         spare_cap = capacity_spare_wake(i, p);
 
                         if (spare_cap > max_spare_cap)
                                 max_spare_cap = spare_cap;
                 }
 
                 /* Adjust by relative CPU capacity of the group */
                 avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
                                         group->sgc->capacity;
                 runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
                                         group->sgc->capacity;
 
                 if (local_group) {
                         this_runnable_load = runnable_load;
                         this_avg_load = avg_load;
                         this_spare = max_spare_cap;
                 } else {
                         if (min_runnable_load > (runnable_load + imbalance)) {
                                 /*
                                  * The runnable load is significantly smaller
                                  * so we can pick this new CPU:
                                  */
                                 min_runnable_load = runnable_load;
                                 min_avg_load = avg_load;
                                 idlest = group;
                         } else if ((runnable_load < (min_runnable_load + imbalance)) &&
                                    (100*min_avg_load > imbalance_scale*avg_load)) {
                                 /*
                                  * The runnable loads are close so take the
                                  * blocked load into account through avg_load:
                                  */
                                 min_avg_load = avg_load;
                                 idlest = group;
                         }
 
                         if (most_spare < max_spare_cap) {
                                 most_spare = max_spare_cap;
                                 most_spare_sg = group;
                         }
                 }
         } while (group = group->next, group != sd->groups);
 
         /*
          * The cross-over point between using spare capacity or least load
          * is too conservative for high utilization tasks on partially
          * utilized systems if we require spare_capacity > task_util(p),
          * so we allow for some task stuffing by using
          * spare_capacity > task_util(p)/2.
          *
          * Spare capacity can't be used for fork because the utilization has
          * not been set yet, we must first select a rq to compute the initial
          * utilization.
          */
         if (sd_flag & SD_BALANCE_FORK)
                 goto skip_spare;
 
         if (this_spare > task_util(p) / 2 &&
             imbalance_scale*this_spare > 100*most_spare)
                 return NULL;
 
         if (most_spare > task_util(p) / 2)
                 return most_spare_sg;
 
 skip_spare:
         if (!idlest)
                 return NULL;
 
         /*
          * When comparing groups across NUMA domains, it's possible for the
          * local domain to be very lightly loaded relative to the remote
          * domains but "imbalance" skews the comparison making remote CPUs
          * look much more favourable. When considering cross-domain, add
          * imbalance to the runnable load on the remote node and consider
          * staying local.
          */
         if ((sd->flags & SD_NUMA) &&
             min_runnable_load + imbalance >= this_runnable_load)
                 return NULL;
 
         if (min_runnable_load > (this_runnable_load + imbalance))
                 return NULL;
 
         if ((this_runnable_load < (min_runnable_load + imbalance)) &&
              (100*this_avg_load < imbalance_scale*min_avg_load))
                 return NULL;
 
         return idlest;
 }
 
 /*
  * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
  */
 static int
 find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 {
         unsigned long load, min_load = ULONG_MAX;
         unsigned int min_exit_latency = UINT_MAX;
         u64 latest_idle_timestamp = 0;
         int least_loaded_cpu = this_cpu;
         int shallowest_idle_cpu = -1;
         int i;
 
         /* Check if we have any choice: */
         if (group->group_weight == 1)
                 return cpumask_first(sched_group_span(group));
 
         /* Traverse only the allowed CPUs */
         for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
                 if (idle_cpu(i)) {
                         struct rq *rq = cpu_rq(i);
                         struct cpuidle_state *idle = idle_get_state(rq);
                         if (idle && idle->exit_latency < min_exit_latency) {
                                 /*
                                  * We give priority to a CPU whose idle state
                                  * has the smallest exit latency irrespective
                                  * of any idle timestamp.
                                  */
                                 min_exit_latency = idle->exit_latency;
                                 latest_idle_timestamp = rq->idle_stamp;
                                 shallowest_idle_cpu = i;
                         } else if ((!idle || idle->exit_latency == min_exit_latency) &&
                                    rq->idle_stamp > latest_idle_timestamp) {
                                 /*
                                  * If equal or no active idle state, then
                                  * the most recently idled CPU might have
                                  * a warmer cache.
                                  */
                                 latest_idle_timestamp = rq->idle_stamp;
                                 shallowest_idle_cpu = i;
                         }
                 } else if (shallowest_idle_cpu == -1) {
                         load = weighted_cpuload(cpu_rq(i));
                         if (load < min_load) {
                                 min_load = load;
                                 least_loaded_cpu = i;
                         }
                 }
         }
 
         return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
 }
 
 static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
                                   int cpu, int prev_cpu, int sd_flag)
 {
         int new_cpu = cpu;
 
         if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
                 return prev_cpu;
 
         while (sd) {
                 struct sched_group *group;
                 struct sched_domain *tmp;
                 int weight;
 
                 if (!(sd->flags & sd_flag)) {
                         sd = sd->child;
                         continue;
                 }
 
                 group = find_idlest_group(sd, p, cpu, sd_flag);
                 if (!group) {
                         sd = sd->child;
                         continue;
                 }
 
                 new_cpu = find_idlest_group_cpu(group, p, cpu);
                 if (new_cpu == cpu) {
                         /* Now try balancing at a lower domain level of 'cpu': */
                         sd = sd->child;
                         continue;
                 }
 
                 /* Now try balancing at a lower domain level of 'new_cpu': */
                 cpu = new_cpu;
                 weight = sd->span_weight;
                 sd = NULL;
                 for_each_domain(cpu, tmp) {
                         if (weight <= tmp->span_weight)
                                 break;
                         if (tmp->flags & sd_flag)
                                 sd = tmp;
                 }
         }
 
         return new_cpu;
 }
 
 #ifdef CONFIG_SCHED_SMT
 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
 
 static inline void set_idle_cores(int cpu, int val)
 {
         struct sched_domain_shared *sds;
 
         sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
         if (sds)
                 WRITE_ONCE(sds->has_idle_cores, val);
 }
 
 static inline bool test_idle_cores(int cpu, bool def)
 {
         struct sched_domain_shared *sds;
 
         sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
         if (sds)
                 return READ_ONCE(sds->has_idle_cores);
 
         return def;
 }
 
 /*
  * Scans the local SMT mask to see if the entire core is idle, and records this
  * information in sd_llc_shared->has_idle_cores.
  *
  * Since SMT siblings share all cache levels, inspecting this limited remote
  * state should be fairly cheap.
  */
 void __update_idle_core(struct rq *rq)
 {
         int core = cpu_of(rq);
         int cpu;
 
         rcu_read_lock();
         if (test_idle_cores(core, true))
                 goto unlock;
 
         for_each_cpu(cpu, cpu_smt_mask(core)) {
                 if (cpu == core)
                         continue;
 
                 if (!idle_cpu(cpu))
                         goto unlock;
         }
 
         set_idle_cores(core, 1);
 unlock:
         rcu_read_unlock();
 }
 
 /*
  * Scan the entire LLC domain for idle cores; this dynamically switches off if
  * there are no idle cores left in the system; tracked through
  * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
  */
 static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
 {
         struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
         int core, cpu;
 
         if (!static_branch_likely(&sched_smt_present))
                 return -1;
 
         if (!test_idle_cores(target, false))
                 return -1;
 
         cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
 
         for_each_cpu_wrap(core, cpus, target) {
                 bool idle = true;
 
                 for_each_cpu(cpu, cpu_smt_mask(core)) {
                         cpumask_clear_cpu(cpu, cpus);
                         if (!idle_cpu(cpu))
                                 idle = false;
                 }
 
                 if (idle)
                         return core;
         }
 
         /*
          * Failed to find an idle core; stop looking for one.
          */
         set_idle_cores(target, 0);
 
         return -1;
 }
 
 /*
  * Scan the local SMT mask for idle CPUs.
  */
 static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
         int cpu;
 
         if (!static_branch_likely(&sched_smt_present))
                 return -1;
 
         for_each_cpu(cpu, cpu_smt_mask(target)) {
                 if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
                         continue;
                 if (idle_cpu(cpu))
                         return cpu;
         }
 
         return -1;
 }
 
 #else /* CONFIG_SCHED_SMT */
 
 static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
 {
         return -1;
 }
 
 static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
         return -1;
 }
 
 #endif /* CONFIG_SCHED_SMT */
 
 /*
  * Scan the LLC domain for idle CPUs; this is dynamically regulated by
  * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
  * average idle time for this rq (as found in rq->avg_idle).
  */
 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
 {
         struct sched_domain *this_sd;
         u64 avg_cost, avg_idle;
         u64 time, cost;
         s64 delta;
         int cpu, nr = INT_MAX;
 
         this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
         if (!this_sd)
                 return -1;
 
         /*
          * Due to large variance we need a large fuzz factor; hackbench in
          * particularly is sensitive here.
          */
         avg_idle = this_rq()->avg_idle / 512;
         avg_cost = this_sd->avg_scan_cost + 1;
 
         if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
                 return -1;
 
         if (sched_feat(SIS_PROP)) {
                 u64 span_avg = sd->span_weight * avg_idle;
                 if (span_avg > 4*avg_cost)
                         nr = div_u64(span_avg, avg_cost);
                 else
                         nr = 4;
         }
 
         time = local_clock();
 
         for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
                 if (!--nr)
                         return -1;
                 if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
                         continue;
                 if (idle_cpu(cpu))
                         break;
         }
 
         time = local_clock() - time;
         cost = this_sd->avg_scan_cost;
         delta = (s64)(time - cost) / 8;
         this_sd->avg_scan_cost += delta;
 
         return cpu;
 }
 
 /*
  * Try and locate an idle core/thread in the LLC cache domain.
  */
 static int select_idle_sibling(struct task_struct *p, int prev, int target)
 {
         struct sched_domain *sd;
         int i, recent_used_cpu;
 
         if (idle_cpu(target))
                 return target;
 
         /*
          * If the previous CPU is cache affine and idle, don't be stupid:
          */
         if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
                 return prev;
 
         /* Check a recently used CPU as a potential idle candidate: */
         recent_used_cpu = p->recent_used_cpu;
         if (recent_used_cpu != prev &&
             recent_used_cpu != target &&
             cpus_share_cache(recent_used_cpu, target) &&
             idle_cpu(recent_used_cpu) &&
             cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
                 /*
                  * Replace recent_used_cpu with prev as it is a potential
                  * candidate for the next wake:
                  */
                 p->recent_used_cpu = prev;
                 return recent_used_cpu;
         }
 
         sd = rcu_dereference(per_cpu(sd_llc, target));
         if (!sd)
                 return target;
 
         i = select_idle_core(p, sd, target);
         if ((unsigned)i < nr_cpumask_bits)
                 return i;
 
         i = select_idle_cpu(p, sd, target);
         if ((unsigned)i < nr_cpumask_bits)
                 return i;
 
         i = select_idle_smt(p, sd, target);