kernel/latencytop.c

   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 #include <linux/latencytop.h>
  13 #include <linux/kallsyms.h>
  14 #include <linux/seq_file.h>
  15 #include <linux/notifier.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/proc_fs.h>
  18 #include <linux/module.h>
  19 #include <linux/sched.h>
  20 #include <linux/list.h>
  21 #include <linux/slab.h>
  22 #include <linux/stacktrace.h>
  23
  24 static DEFINE_SPINLOCK(latency_lock);
  25
  26 #define MAXLR 128
  27 static struct latency_record latency_record[MAXLR];
  28
  29 int latencytop_enabled;
  30
  31 void clear_all_latency_tracing(struct task_struct *p)
  32 {
  33         unsigned long flags;
  34
  35         if (!latencytop_enabled)
  36                 return;
  37
  38         spin_lock_irqsave(&latency_lock, flags);
  39         memset(&p->latency_record, 0, sizeof(p->latency_record));
  40         p->latency_record_count = 0;
  41         spin_unlock_irqrestore(&latency_lock, flags);
  42 }
  43
  44 static void clear_global_latency_tracing(void)
  45 {
  46         unsigned long flags;
  47
  48         spin_lock_irqsave(&latency_lock, flags);
  49         memset(&latency_record, 0, sizeof(latency_record));
  50         spin_unlock_irqrestore(&latency_lock, flags);
  51 }
  52
  53 static void __sched
  54 account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
  55 {
  56         int firstnonnull = MAXLR + 1;
  57         int i;
  58
  59         if (!latencytop_enabled)
  60                 return;
  61
  62         /* skip kernel threads for now */
  63         if (!tsk->mm)
  64                 return;
  65
  66         for (i = 0; i < MAXLR; i++) {
  67                 int q;
  68                 int same = 1;
  69                 /* Nothing stored: */
  70                 if (!latency_record[i].backtrace[0]) {
  71                         if (firstnonnull > i)
  72                                 firstnonnull = i;
  73                         continue;
  74                 }
  75                 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
  76                         if (latency_record[i].backtrace[q] !=
  77                                 lat->backtrace[q])
  78                                 same = 0;
  79                         if (same && lat->backtrace[q] == 0)
  80                                 break;
  81                         if (same && lat->backtrace[q] == ULONG_MAX)
  82                                 break;
  83                 }
  84                 if (same) {
  85                         latency_record[i].count++;
  86                         latency_record[i].time += lat->time;
  87                         if (lat->time > latency_record[i].max)
  88                                 latency_record[i].max = lat->time;
  89                         return;
  90                 }
  91         }
  92
  93         i = firstnonnull;
  94         if (i >= MAXLR - 1)
  95                 return;
  96
  97         /* Allocted a new one: */
  98         memcpy(&latency_record[i], lat, sizeof(struct latency_record));
  99 }
 100
 101 static inline void store_stacktrace(struct task_struct *tsk, struct latency_record *lat)
 102 {
 103         struct stack_trace trace;
 104
 105         memset(&trace, 0, sizeof(trace));
 106         trace.max_entries = LT_BACKTRACEDEPTH;
 107         trace.entries = &lat->backtrace[0];
 108         trace.skip = 0;
 109         save_stack_trace_tsk(tsk, &trace);
 110 }
 111
 112 void __sched
 113 account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
 114 {
 115         unsigned long flags;
 116         int i, q;
 117         struct latency_record lat;
 118
 119         if (!latencytop_enabled)
 120                 return;
 121
 122         /* Long interruptible waits are generally user requested... */
 123         if (inter && usecs > 5000)
 124                 return;
 125
 126         memset(&lat, 0, sizeof(lat));
 127         lat.count = 1;
 128         lat.time = usecs;
 129         lat.max = usecs;
 130         store_stacktrace(tsk, &lat);
 131
 132         spin_lock_irqsave(&latency_lock, flags);
 133
 134         account_global_scheduler_latency(tsk, &lat);
 135
 136         /*
 137          * short term hack; if we're > 32 we stop; future we recycle:
 138          */
 139         tsk->latency_record_count++;
 140         if (tsk->latency_record_count >= LT_SAVECOUNT)
 141                 goto out_unlock;
 142
 143         for (i = 0; i < LT_SAVECOUNT ; i++) {
 144                 struct latency_record *mylat;
 145                 int same = 1;
 146                 mylat = &tsk->latency_record[i];
 147                 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
 148                         if (mylat->backtrace[q] !=
 149                                 lat.backtrace[q])
 150                                 same = 0;
 151                         if (same && lat.backtrace[q] == 0)
 152                                 break;
 153                         if (same && lat.backtrace[q] == ULONG_MAX)
 154                                 break;
 155                 }
 156                 if (same) {
 157                         mylat->count++;
 158                         mylat->time += lat.time;
 159                         if (lat.time > mylat->max)
 160                                 mylat->max = lat.time;
 161                         goto out_unlock;
 162                 }
 163         }
 164
 165         /* Allocated a new one: */
 166         i = tsk->latency_record_count;
 167         memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
 168
 169 out_unlock:
 170         spin_unlock_irqrestore(&latency_lock, flags);
 171 }
 172
 173 static int lstats_show(struct seq_file *m, void *v)
 174 {
 175         int i;
 176
 177         seq_puts(m, "Latency Top version : v0.1\n");
 178
 179         for (i = 0; i < MAXLR; i++) {
 180                 if (latency_record[i].backtrace[0]) {
 181                         int q;
 182                         seq_printf(m, "%i %li %li ",
 183                                 latency_record[i].count,
 184                                 latency_record[i].time,
 185                                 latency_record[i].max);
 186                         for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
 187                                 char sym[KSYM_NAME_LEN];
 188                                 char *c;
 189                                 if (!latency_record[i].backtrace[q])
 190                                         break;
 191                                 if (latency_record[i].backtrace[q] == ULONG_MAX)
 192                                         break;
 193                                 sprint_symbol(sym, latency_record[i].backtrace[q]);
 194                                 c = strchr(sym, '+');
 195                                 if (c)
 196                                         *c = 0;
 197                                 seq_printf(m, "%s ", sym);
 198                         }
 199                         seq_printf(m, "\n");
 200                 }
 201         }
 202         return 0;
 203 }
 204
 205 static ssize_t
 206 lstats_write(struct file *file, const char __user *buf, size_t count,
 207              loff_t *offs)
 208 {
 209         clear_global_latency_tracing();
 210
 211         return count;
 212 }
 213
 214 static int lstats_open(struct inode *inode, struct file *filp)
 215 {
 216         return single_open(filp, lstats_show, NULL);
 217 }
 218
 219 static struct file_operations lstats_fops = {
 220         .open           = lstats_open,
 221         .read           = seq_read,
 222         .write          = lstats_write,
 223         .llseek         = seq_lseek,
 224         .release        = single_release,
 225 };
 226
 227 static int __init init_lstats_procfs(void)
 228 {
 229         struct proc_dir_entry *pe;
 230
 231         pe = create_proc_entry("latency_stats", 0644, NULL);
 232         if (!pe)
 233                 return -ENOMEM;
 234
 235         pe->proc_fops = &lstats_fops;
 236
 237         return 0;
 238 }
 239 __initcall(init_lstats_procfs);