~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/latencytop.c

Version: ~ [ linux-5.11-rc3 ] ~ [ linux-5.10.7 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.89 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.167 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.215 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.251 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.251 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.85 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * latencytop.c: Latency display infrastructure
  3  *
  4  * (C) Copyright 2008 Intel Corporation
  5  * Author: Arjan van de Ven <arjan@linux.intel.com>
  6  *
  7  * This program is free software; you can redistribute it and/or
  8  * modify it under the terms of the GNU General Public License
  9  * as published by the Free Software Foundation; version 2
 10  * of the License.
 11  */
 12 
 13 /*
 14  * CONFIG_LATENCYTOP enables a kernel latency tracking infrastructure that is
 15  * used by the "latencytop" userspace tool. The latency that is tracked is not
 16  * the 'traditional' interrupt latency (which is primarily caused by something
 17  * else consuming CPU), but instead, it is the latency an application encounters
 18  * because the kernel sleeps on its behalf for various reasons.
 19  *
 20  * This code tracks 2 levels of statistics:
 21  * 1) System level latency
 22  * 2) Per process latency
 23  *
 24  * The latency is stored in fixed sized data structures in an accumulated form;
 25  * if the "same" latency cause is hit twice, this will be tracked as one entry
 26  * in the data structure. Both the count, total accumulated latency and maximum
 27  * latency are tracked in this data structure. When the fixed size structure is
 28  * full, no new causes are tracked until the buffer is flushed by writing to
 29  * the /proc file; the userspace tool does this on a regular basis.
 30  *
 31  * A latency cause is identified by a stringified backtrace at the point that
 32  * the scheduler gets invoked. The userland tool will use this string to
 33  * identify the cause of the latency in human readable form.
 34  *
 35  * The information is exported via /proc/latency_stats and /proc/<pid>/latency.
 36  * These files look like this:
 37  *
 38  * Latency Top version : v0.1
 39  * 70 59433 4897 i915_irq_wait drm_ioctl vfs_ioctl do_vfs_ioctl sys_ioctl
 40  * |    |    |    |
 41  * |    |    |    +----> the stringified backtrace
 42  * |    |    +---------> The maximum latency for this entry in microseconds
 43  * |    +--------------> The accumulated latency for this entry (microseconds)
 44  * +-------------------> The number of times this entry is hit
 45  *
 46  * (note: the average latency is the accumulated latency divided by the number
 47  * of times)
 48  */
 49 
 50 #include <linux/latencytop.h>
 51 #include <linux/kallsyms.h>
 52 #include <linux/seq_file.h>
 53 #include <linux/notifier.h>
 54 #include <linux/spinlock.h>
 55 #include <linux/proc_fs.h>
 56 #include <linux/export.h>
 57 #include <linux/sched.h>
 58 #include <linux/list.h>
 59 #include <linux/stacktrace.h>
 60 
 61 static DEFINE_RAW_SPINLOCK(latency_lock);
 62 
 63 #define MAXLR 128
 64 static struct latency_record latency_record[MAXLR];
 65 
 66 int latencytop_enabled;
 67 
 68 void clear_all_latency_tracing(struct task_struct *p)
 69 {
 70         unsigned long flags;
 71 
 72         if (!latencytop_enabled)
 73                 return;
 74 
 75         raw_spin_lock_irqsave(&latency_lock, flags);
 76         memset(&p->latency_record, 0, sizeof(p->latency_record));
 77         p->latency_record_count = 0;
 78         raw_spin_unlock_irqrestore(&latency_lock, flags);
 79 }
 80 
 81 static void clear_global_latency_tracing(void)
 82 {
 83         unsigned long flags;
 84 
 85         raw_spin_lock_irqsave(&latency_lock, flags);
 86         memset(&latency_record, 0, sizeof(latency_record));
 87         raw_spin_unlock_irqrestore(&latency_lock, flags);
 88 }
 89 
 90 static void __sched
 91 account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
 92 {
 93         int firstnonnull = MAXLR + 1;
 94         int i;
 95 
 96         if (!latencytop_enabled)
 97                 return;
 98 
 99         /* skip kernel threads for now */
100         if (!tsk->mm)
101                 return;
102 
103         for (i = 0; i < MAXLR; i++) {
104                 int q, same = 1;
105 
106                 /* Nothing stored: */
107                 if (!latency_record[i].backtrace[0]) {
108                         if (firstnonnull > i)
109                                 firstnonnull = i;
110                         continue;
111                 }
112                 for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
113                         unsigned long record = lat->backtrace[q];
114 
115                         if (latency_record[i].backtrace[q] != record) {
116                                 same = 0;
117                                 break;
118                         }
119 
120                         /* 0 and ULONG_MAX entries mean end of backtrace: */
121                         if (record == 0 || record == ULONG_MAX)
122                                 break;
123                 }
124                 if (same) {
125                         latency_record[i].count++;
126                         latency_record[i].time += lat->time;
127                         if (lat->time > latency_record[i].max)
128                                 latency_record[i].max = lat->time;
129                         return;
130                 }
131         }
132 
133         i = firstnonnull;
134         if (i >= MAXLR - 1)
135                 return;
136 
137         /* Allocted a new one: */
138         memcpy(&latency_record[i], lat, sizeof(struct latency_record));
139 }
140 
141 /*
142  * Iterator to store a backtrace into a latency record entry
143  */
144 static inline void store_stacktrace(struct task_struct *tsk,
145                                         struct latency_record *lat)
146 {
147         struct stack_trace trace;
148 
149         memset(&trace, 0, sizeof(trace));
150         trace.max_entries = LT_BACKTRACEDEPTH;
151         trace.entries = &lat->backtrace[0];
152         save_stack_trace_tsk(tsk, &trace);
153 }
154 
155 /**
156  * __account_scheduler_latency - record an occurred latency
157  * @tsk - the task struct of the task hitting the latency
158  * @usecs - the duration of the latency in microseconds
159  * @inter - 1 if the sleep was interruptible, 0 if uninterruptible
160  *
161  * This function is the main entry point for recording latency entries
162  * as called by the scheduler.
163  *
164  * This function has a few special cases to deal with normal 'non-latency'
165  * sleeps: specifically, interruptible sleep longer than 5 msec is skipped
166  * since this usually is caused by waiting for events via select() and co.
167  *
168  * Negative latencies (caused by time going backwards) are also explicitly
169  * skipped.
170  */
171 void __sched
172 __account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
173 {
174         unsigned long flags;
175         int i, q;
176         struct latency_record lat;
177 
178         /* Long interruptible waits are generally user requested... */
179         if (inter && usecs > 5000)
180                 return;
181 
182         /* Negative sleeps are time going backwards */
183         /* Zero-time sleeps are non-interesting */
184         if (usecs <= 0)
185                 return;
186 
187         memset(&lat, 0, sizeof(lat));
188         lat.count = 1;
189         lat.time = usecs;
190         lat.max = usecs;
191         store_stacktrace(tsk, &lat);
192 
193         raw_spin_lock_irqsave(&latency_lock, flags);
194 
195         account_global_scheduler_latency(tsk, &lat);
196 
197         for (i = 0; i < tsk->latency_record_count; i++) {
198                 struct latency_record *mylat;
199                 int same = 1;
200 
201                 mylat = &tsk->latency_record[i];
202                 for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
203                         unsigned long record = lat.backtrace[q];
204 
205                         if (mylat->backtrace[q] != record) {
206                                 same = 0;
207                                 break;
208                         }
209 
210                         /* 0 and ULONG_MAX entries mean end of backtrace: */
211                         if (record == 0 || record == ULONG_MAX)
212                                 break;
213                 }
214                 if (same) {
215                         mylat->count++;
216                         mylat->time += lat.time;
217                         if (lat.time > mylat->max)
218                                 mylat->max = lat.time;
219                         goto out_unlock;
220                 }
221         }
222 
223         /*
224          * short term hack; if we're > 32 we stop; future we recycle:
225          */
226         if (tsk->latency_record_count >= LT_SAVECOUNT)
227                 goto out_unlock;
228 
229         /* Allocated a new one: */
230         i = tsk->latency_record_count++;
231         memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
232 
233 out_unlock:
234         raw_spin_unlock_irqrestore(&latency_lock, flags);
235 }
236 
237 static int lstats_show(struct seq_file *m, void *v)
238 {
239         int i;
240 
241         seq_puts(m, "Latency Top version : v0.1\n");
242 
243         for (i = 0; i < MAXLR; i++) {
244                 struct latency_record *lr = &latency_record[i];
245 
246                 if (lr->backtrace[0]) {
247                         int q;
248                         seq_printf(m, "%i %lu %lu",
249                                    lr->count, lr->time, lr->max);
250                         for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
251                                 unsigned long bt = lr->backtrace[q];
252                                 if (!bt)
253                                         break;
254                                 if (bt == ULONG_MAX)
255                                         break;
256                                 seq_printf(m, " %ps", (void *)bt);
257                         }
258                         seq_printf(m, "\n");
259                 }
260         }
261         return 0;
262 }
263 
264 static ssize_t
265 lstats_write(struct file *file, const char __user *buf, size_t count,
266              loff_t *offs)
267 {
268         clear_global_latency_tracing();
269 
270         return count;
271 }
272 
273 static int lstats_open(struct inode *inode, struct file *filp)
274 {
275         return single_open(filp, lstats_show, NULL);
276 }
277 
278 static const struct file_operations lstats_fops = {
279         .open           = lstats_open,
280         .read           = seq_read,
281         .write          = lstats_write,
282         .llseek         = seq_lseek,
283         .release        = single_release,
284 };
285 
286 static int __init init_lstats_procfs(void)
287 {
288         proc_create("latency_stats", 0644, NULL, &lstats_fops);
289         return 0;
290 }
291 device_initcall(init_lstats_procfs);
292 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp