kernel/delayacct.c

   1 /* delayacct.c - per-task delay accounting
   2  *
   3  * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   4  *
   5  * This program is free software;  you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it would be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
  13  * the GNU General Public License for more details.
  14  */
  15
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18 #include <linux/time.h>
  19 #include <linux/sysctl.h>
  20 #include <linux/delayacct.h>
  21
  22 int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  23 kmem_cache_t *delayacct_cache;
  24
  25 static int __init delayacct_setup_disable(char *str)
  26 {
  27         delayacct_on = 0;
  28         return 1;
  29 }
  30 __setup("nodelayacct", delayacct_setup_disable);
  31
  32 void delayacct_init(void)
  33 {
  34         delayacct_cache = kmem_cache_create("delayacct_cache",
  35                                         sizeof(struct task_delay_info),
  36                                         0,
  37                                         SLAB_PANIC,
  38                                         NULL, NULL);
  39         delayacct_tsk_init(&init_task);
  40 }
  41
  42 void __delayacct_tsk_init(struct task_struct *tsk)
  43 {
  44         tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
  45         if (tsk->delays)
  46                 spin_lock_init(&tsk->delays->lock);
  47 }
  48
  49 /*
  50  * Start accounting for a delay statistic using
  51  * its starting timestamp (@start)
  52  */
  53
  54 static inline void delayacct_start(struct timespec *start)
  55 {
  56         do_posix_clock_monotonic_gettime(start);
  57 }
  58
  59 /*
  60  * Finish delay accounting for a statistic using
  61  * its timestamps (@start, @end), accumalator (@total) and @count
  62  */
  63
  64 static void delayacct_end(struct timespec *start, struct timespec *end,
  65                                 u64 *total, u32 *count)
  66 {
  67         struct timespec ts;
  68         s64 ns;
  69
  70         do_posix_clock_monotonic_gettime(end);
  71         ts = timespec_sub(*end, *start);
  72         ns = timespec_to_ns(&ts);
  73         if (ns < 0)
  74                 return;
  75
  76         spin_lock(&current->delays->lock);
  77         *total += ns;
  78         (*count)++;
  79         spin_unlock(&current->delays->lock);
  80 }
  81
  82 void __delayacct_blkio_start(void)
  83 {
  84         delayacct_start(&current->delays->blkio_start);
  85 }
  86
  87 void __delayacct_blkio_end(void)
  88 {
  89         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  90                 /* Swapin block I/O */
  91                 delayacct_end(&current->delays->blkio_start,
  92                         &current->delays->blkio_end,
  93                         &current->delays->swapin_delay,
  94                         &current->delays->swapin_count);
  95         else    /* Other block I/O */
  96                 delayacct_end(&current->delays->blkio_start,
  97                         &current->delays->blkio_end,
  98                         &current->delays->blkio_delay,
  99                         &current->delays->blkio_count);
 100 }
 101
 102 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 103 {
 104         s64 tmp;
 105         struct timespec ts;
 106         unsigned long t1,t2,t3;
 107
 108         /* Though tsk->delays accessed later, early exit avoids
 109          * unnecessary returning of other data
 110          */
 111         if (!tsk->delays)
 112                 goto done;
 113
 114         tmp = (s64)d->cpu_run_real_total;
 115         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
 116         tmp += timespec_to_ns(&ts);
 117         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 118
 119         /*
 120          * No locking available for sched_info (and too expensive to add one)
 121          * Mitigate by taking snapshot of values
 122          */
 123         t1 = tsk->sched_info.pcnt;
 124         t2 = tsk->sched_info.run_delay;
 125         t3 = tsk->sched_info.cpu_time;
 126
 127         d->cpu_count += t1;
 128
 129         jiffies_to_timespec(t2, &ts);
 130         tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
 131         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 132
 133         tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
 134         d->cpu_run_virtual_total =
 135                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 136
 137         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 138
 139         spin_lock(&tsk->delays->lock);
 140         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 141         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 142         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 143         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 144         d->blkio_count += tsk->delays->blkio_count;
 145         d->swapin_count += tsk->delays->swapin_count;
 146         spin_unlock(&tsk->delays->lock);
 147
 148 done:
 149         return 0;
 150 }
 151
 152 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 153 {
 154         __u64 ret;
 155
 156         spin_lock(&tsk->delays->lock);
 157         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 158                                 tsk->delays->swapin_delay);
 159         spin_unlock(&tsk->delays->lock);
 160         return ret;
 161 }
 162