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Linux/kernel/profile.c

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  1 /*
  2  *  linux/kernel/profile.c
  3  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
  4  *  with configurable resolution, support for restricting the cpus on
  5  *  which profiling is done, and switching between cpu time and
  6  *  schedule() calls via kernel command line parameters passed at boot.
  7  *
  8  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
  9  *      Red Hat, July 2004
 10  *  Consolidation of architecture support code for profiling,
 11  *      Nadia Yvette Chambers, Oracle, July 2004
 12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
 13  *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
 14  *      Oracle, 2004
 15  */
 16 
 17 #include <linux/export.h>
 18 #include <linux/profile.h>
 19 #include <linux/bootmem.h>
 20 #include <linux/notifier.h>
 21 #include <linux/mm.h>
 22 #include <linux/cpumask.h>
 23 #include <linux/cpu.h>
 24 #include <linux/highmem.h>
 25 #include <linux/mutex.h>
 26 #include <linux/slab.h>
 27 #include <linux/vmalloc.h>
 28 #include <linux/sched/stat.h>
 29 
 30 #include <asm/sections.h>
 31 #include <asm/irq_regs.h>
 32 #include <asm/ptrace.h>
 33 
 34 struct profile_hit {
 35         u32 pc, hits;
 36 };
 37 #define PROFILE_GRPSHIFT        3
 38 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
 39 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
 40 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
 41 
 42 static atomic_t *prof_buffer;
 43 static unsigned long prof_len, prof_shift;
 44 
 45 int prof_on __read_mostly;
 46 EXPORT_SYMBOL_GPL(prof_on);
 47 
 48 static cpumask_var_t prof_cpu_mask;
 49 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 50 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
 51 static DEFINE_PER_CPU(int, cpu_profile_flip);
 52 static DEFINE_MUTEX(profile_flip_mutex);
 53 #endif /* CONFIG_SMP */
 54 
 55 int profile_setup(char *str)
 56 {
 57         static const char schedstr[] = "schedule";
 58         static const char sleepstr[] = "sleep";
 59         static const char kvmstr[] = "kvm";
 60         int par;
 61 
 62         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
 63 #ifdef CONFIG_SCHEDSTATS
 64                 force_schedstat_enabled();
 65                 prof_on = SLEEP_PROFILING;
 66                 if (str[strlen(sleepstr)] == ',')
 67                         str += strlen(sleepstr) + 1;
 68                 if (get_option(&str, &par))
 69                         prof_shift = par;
 70                 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
 71                         prof_shift);
 72 #else
 73                 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
 74 #endif /* CONFIG_SCHEDSTATS */
 75         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
 76                 prof_on = SCHED_PROFILING;
 77                 if (str[strlen(schedstr)] == ',')
 78                         str += strlen(schedstr) + 1;
 79                 if (get_option(&str, &par))
 80                         prof_shift = par;
 81                 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
 82                         prof_shift);
 83         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
 84                 prof_on = KVM_PROFILING;
 85                 if (str[strlen(kvmstr)] == ',')
 86                         str += strlen(kvmstr) + 1;
 87                 if (get_option(&str, &par))
 88                         prof_shift = par;
 89                 pr_info("kernel KVM profiling enabled (shift: %ld)\n",
 90                         prof_shift);
 91         } else if (get_option(&str, &par)) {
 92                 prof_shift = par;
 93                 prof_on = CPU_PROFILING;
 94                 pr_info("kernel profiling enabled (shift: %ld)\n",
 95                         prof_shift);
 96         }
 97         return 1;
 98 }
 99 __setup("profile=", profile_setup);
100 
101 
102 int __ref profile_init(void)
103 {
104         int buffer_bytes;
105         if (!prof_on)
106                 return 0;
107 
108         /* only text is profiled */
109         prof_len = (_etext - _stext) >> prof_shift;
110         buffer_bytes = prof_len*sizeof(atomic_t);
111 
112         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
113                 return -ENOMEM;
114 
115         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
116 
117         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
118         if (prof_buffer)
119                 return 0;
120 
121         prof_buffer = alloc_pages_exact(buffer_bytes,
122                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
123         if (prof_buffer)
124                 return 0;
125 
126         prof_buffer = vzalloc(buffer_bytes);
127         if (prof_buffer)
128                 return 0;
129 
130         free_cpumask_var(prof_cpu_mask);
131         return -ENOMEM;
132 }
133 
134 /* Profile event notifications */
135 
136 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
137 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
138 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
139 
140 void profile_task_exit(struct task_struct *task)
141 {
142         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
143 }
144 
145 int profile_handoff_task(struct task_struct *task)
146 {
147         int ret;
148         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
149         return (ret == NOTIFY_OK) ? 1 : 0;
150 }
151 
152 void profile_munmap(unsigned long addr)
153 {
154         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
155 }
156 
157 int task_handoff_register(struct notifier_block *n)
158 {
159         return atomic_notifier_chain_register(&task_free_notifier, n);
160 }
161 EXPORT_SYMBOL_GPL(task_handoff_register);
162 
163 int task_handoff_unregister(struct notifier_block *n)
164 {
165         return atomic_notifier_chain_unregister(&task_free_notifier, n);
166 }
167 EXPORT_SYMBOL_GPL(task_handoff_unregister);
168 
169 int profile_event_register(enum profile_type type, struct notifier_block *n)
170 {
171         int err = -EINVAL;
172 
173         switch (type) {
174         case PROFILE_TASK_EXIT:
175                 err = blocking_notifier_chain_register(
176                                 &task_exit_notifier, n);
177                 break;
178         case PROFILE_MUNMAP:
179                 err = blocking_notifier_chain_register(
180                                 &munmap_notifier, n);
181                 break;
182         }
183 
184         return err;
185 }
186 EXPORT_SYMBOL_GPL(profile_event_register);
187 
188 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
189 {
190         int err = -EINVAL;
191 
192         switch (type) {
193         case PROFILE_TASK_EXIT:
194                 err = blocking_notifier_chain_unregister(
195                                 &task_exit_notifier, n);
196                 break;
197         case PROFILE_MUNMAP:
198                 err = blocking_notifier_chain_unregister(
199                                 &munmap_notifier, n);
200                 break;
201         }
202 
203         return err;
204 }
205 EXPORT_SYMBOL_GPL(profile_event_unregister);
206 
207 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
208 /*
209  * Each cpu has a pair of open-addressed hashtables for pending
210  * profile hits. read_profile() IPI's all cpus to request them
211  * to flip buffers and flushes their contents to prof_buffer itself.
212  * Flip requests are serialized by the profile_flip_mutex. The sole
213  * use of having a second hashtable is for avoiding cacheline
214  * contention that would otherwise happen during flushes of pending
215  * profile hits required for the accuracy of reported profile hits
216  * and so resurrect the interrupt livelock issue.
217  *
218  * The open-addressed hashtables are indexed by profile buffer slot
219  * and hold the number of pending hits to that profile buffer slot on
220  * a cpu in an entry. When the hashtable overflows, all pending hits
221  * are accounted to their corresponding profile buffer slots with
222  * atomic_add() and the hashtable emptied. As numerous pending hits
223  * may be accounted to a profile buffer slot in a hashtable entry,
224  * this amortizes a number of atomic profile buffer increments likely
225  * to be far larger than the number of entries in the hashtable,
226  * particularly given that the number of distinct profile buffer
227  * positions to which hits are accounted during short intervals (e.g.
228  * several seconds) is usually very small. Exclusion from buffer
229  * flipping is provided by interrupt disablement (note that for
230  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
231  * process context).
232  * The hash function is meant to be lightweight as opposed to strong,
233  * and was vaguely inspired by ppc64 firmware-supported inverted
234  * pagetable hash functions, but uses a full hashtable full of finite
235  * collision chains, not just pairs of them.
236  *
237  * -- nyc
238  */
239 static void __profile_flip_buffers(void *unused)
240 {
241         int cpu = smp_processor_id();
242 
243         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
244 }
245 
246 static void profile_flip_buffers(void)
247 {
248         int i, j, cpu;
249 
250         mutex_lock(&profile_flip_mutex);
251         j = per_cpu(cpu_profile_flip, get_cpu());
252         put_cpu();
253         on_each_cpu(__profile_flip_buffers, NULL, 1);
254         for_each_online_cpu(cpu) {
255                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
256                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
257                         if (!hits[i].hits) {
258                                 if (hits[i].pc)
259                                         hits[i].pc = 0;
260                                 continue;
261                         }
262                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
263                         hits[i].hits = hits[i].pc = 0;
264                 }
265         }
266         mutex_unlock(&profile_flip_mutex);
267 }
268 
269 static void profile_discard_flip_buffers(void)
270 {
271         int i, cpu;
272 
273         mutex_lock(&profile_flip_mutex);
274         i = per_cpu(cpu_profile_flip, get_cpu());
275         put_cpu();
276         on_each_cpu(__profile_flip_buffers, NULL, 1);
277         for_each_online_cpu(cpu) {
278                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
279                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
280         }
281         mutex_unlock(&profile_flip_mutex);
282 }
283 
284 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
285 {
286         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
287         int i, j, cpu;
288         struct profile_hit *hits;
289 
290         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
291         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
292         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
293         cpu = get_cpu();
294         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
295         if (!hits) {
296                 put_cpu();
297                 return;
298         }
299         /*
300          * We buffer the global profiler buffer into a per-CPU
301          * queue and thus reduce the number of global (and possibly
302          * NUMA-alien) accesses. The write-queue is self-coalescing:
303          */
304         local_irq_save(flags);
305         do {
306                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
307                         if (hits[i + j].pc == pc) {
308                                 hits[i + j].hits += nr_hits;
309                                 goto out;
310                         } else if (!hits[i + j].hits) {
311                                 hits[i + j].pc = pc;
312                                 hits[i + j].hits = nr_hits;
313                                 goto out;
314                         }
315                 }
316                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
317         } while (i != primary);
318 
319         /*
320          * Add the current hit(s) and flush the write-queue out
321          * to the global buffer:
322          */
323         atomic_add(nr_hits, &prof_buffer[pc]);
324         for (i = 0; i < NR_PROFILE_HIT; ++i) {
325                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
326                 hits[i].pc = hits[i].hits = 0;
327         }
328 out:
329         local_irq_restore(flags);
330         put_cpu();
331 }
332 
333 static int profile_dead_cpu(unsigned int cpu)
334 {
335         struct page *page;
336         int i;
337 
338         if (prof_cpu_mask != NULL)
339                 cpumask_clear_cpu(cpu, prof_cpu_mask);
340 
341         for (i = 0; i < 2; i++) {
342                 if (per_cpu(cpu_profile_hits, cpu)[i]) {
343                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
344                         per_cpu(cpu_profile_hits, cpu)[i] = NULL;
345                         __free_page(page);
346                 }
347         }
348         return 0;
349 }
350 
351 static int profile_prepare_cpu(unsigned int cpu)
352 {
353         int i, node = cpu_to_mem(cpu);
354         struct page *page;
355 
356         per_cpu(cpu_profile_flip, cpu) = 0;
357 
358         for (i = 0; i < 2; i++) {
359                 if (per_cpu(cpu_profile_hits, cpu)[i])
360                         continue;
361 
362                 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
363                 if (!page) {
364                         profile_dead_cpu(cpu);
365                         return -ENOMEM;
366                 }
367                 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
368 
369         }
370         return 0;
371 }
372 
373 static int profile_online_cpu(unsigned int cpu)
374 {
375         if (prof_cpu_mask != NULL)
376                 cpumask_set_cpu(cpu, prof_cpu_mask);
377 
378         return 0;
379 }
380 
381 #else /* !CONFIG_SMP */
382 #define profile_flip_buffers()          do { } while (0)
383 #define profile_discard_flip_buffers()  do { } while (0)
384 
385 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
386 {
387         unsigned long pc;
388         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
389         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
390 }
391 #endif /* !CONFIG_SMP */
392 
393 void profile_hits(int type, void *__pc, unsigned int nr_hits)
394 {
395         if (prof_on != type || !prof_buffer)
396                 return;
397         do_profile_hits(type, __pc, nr_hits);
398 }
399 EXPORT_SYMBOL_GPL(profile_hits);
400 
401 void profile_tick(int type)
402 {
403         struct pt_regs *regs = get_irq_regs();
404 
405         if (!user_mode(regs) && prof_cpu_mask != NULL &&
406             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
407                 profile_hit(type, (void *)profile_pc(regs));
408 }
409 
410 #ifdef CONFIG_PROC_FS
411 #include <linux/proc_fs.h>
412 #include <linux/seq_file.h>
413 #include <linux/uaccess.h>
414 
415 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
416 {
417         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
418         return 0;
419 }
420 
421 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
422 {
423         return single_open(file, prof_cpu_mask_proc_show, NULL);
424 }
425 
426 static ssize_t prof_cpu_mask_proc_write(struct file *file,
427         const char __user *buffer, size_t count, loff_t *pos)
428 {
429         cpumask_var_t new_value;
430         int err;
431 
432         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
433                 return -ENOMEM;
434 
435         err = cpumask_parse_user(buffer, count, new_value);
436         if (!err) {
437                 cpumask_copy(prof_cpu_mask, new_value);
438                 err = count;
439         }
440         free_cpumask_var(new_value);
441         return err;
442 }
443 
444 static const struct file_operations prof_cpu_mask_proc_fops = {
445         .open           = prof_cpu_mask_proc_open,
446         .read           = seq_read,
447         .llseek         = seq_lseek,
448         .release        = single_release,
449         .write          = prof_cpu_mask_proc_write,
450 };
451 
452 void create_prof_cpu_mask(void)
453 {
454         /* create /proc/irq/prof_cpu_mask */
455         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
456 }
457 
458 /*
459  * This function accesses profiling information. The returned data is
460  * binary: the sampling step and the actual contents of the profile
461  * buffer. Use of the program readprofile is recommended in order to
462  * get meaningful info out of these data.
463  */
464 static ssize_t
465 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
466 {
467         unsigned long p = *ppos;
468         ssize_t read;
469         char *pnt;
470         unsigned int sample_step = 1 << prof_shift;
471 
472         profile_flip_buffers();
473         if (p >= (prof_len+1)*sizeof(unsigned int))
474                 return 0;
475         if (count > (prof_len+1)*sizeof(unsigned int) - p)
476                 count = (prof_len+1)*sizeof(unsigned int) - p;
477         read = 0;
478 
479         while (p < sizeof(unsigned int) && count > 0) {
480                 if (put_user(*((char *)(&sample_step)+p), buf))
481                         return -EFAULT;
482                 buf++; p++; count--; read++;
483         }
484         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
485         if (copy_to_user(buf, (void *)pnt, count))
486                 return -EFAULT;
487         read += count;
488         *ppos += read;
489         return read;
490 }
491 
492 /*
493  * Writing to /proc/profile resets the counters
494  *
495  * Writing a 'profiling multiplier' value into it also re-sets the profiling
496  * interrupt frequency, on architectures that support this.
497  */
498 static ssize_t write_profile(struct file *file, const char __user *buf,
499                              size_t count, loff_t *ppos)
500 {
501 #ifdef CONFIG_SMP
502         extern int setup_profiling_timer(unsigned int multiplier);
503 
504         if (count == sizeof(int)) {
505                 unsigned int multiplier;
506 
507                 if (copy_from_user(&multiplier, buf, sizeof(int)))
508                         return -EFAULT;
509 
510                 if (setup_profiling_timer(multiplier))
511                         return -EINVAL;
512         }
513 #endif
514         profile_discard_flip_buffers();
515         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
516         return count;
517 }
518 
519 static const struct file_operations proc_profile_operations = {
520         .read           = read_profile,
521         .write          = write_profile,
522         .llseek         = default_llseek,
523 };
524 
525 int __ref create_proc_profile(void)
526 {
527         struct proc_dir_entry *entry;
528 #ifdef CONFIG_SMP
529         enum cpuhp_state online_state;
530 #endif
531 
532         int err = 0;
533 
534         if (!prof_on)
535                 return 0;
536 #ifdef CONFIG_SMP
537         err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
538                                 profile_prepare_cpu, profile_dead_cpu);
539         if (err)
540                 return err;
541 
542         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
543                                 profile_online_cpu, NULL);
544         if (err < 0)
545                 goto err_state_prep;
546         online_state = err;
547         err = 0;
548 #endif
549         entry = proc_create("profile", S_IWUSR | S_IRUGO,
550                             NULL, &proc_profile_operations);
551         if (!entry)
552                 goto err_state_onl;
553         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
554 
555         return err;
556 err_state_onl:
557 #ifdef CONFIG_SMP
558         cpuhp_remove_state(online_state);
559 err_state_prep:
560         cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
561 #endif
562         return err;
563 }
564 subsys_initcall(create_proc_profile);
565 #endif /* CONFIG_PROC_FS */
566 

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