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; /* Delay accounting turned on/off */
  23 kmem_cache_t *delayacct_cache;
  24
  25 static int __init delayacct_setup_enable(char *str)
  26 {
  27         delayacct_on = 1;
  28         return 1;
  29 }
  30 __setup("delayacct", delayacct_setup_enable);
  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         spin_lock_init(&tsk->delays_lock);
  45         /* No need to acquire tsk->delays_lock for allocation here unless
  46            __delayacct_tsk_init called after tsk is attached to tasklist
  47         */
  48         tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
  49         if (tsk->delays)
  50                 spin_lock_init(&tsk->delays->lock);
  51 }
  52
  53 void __delayacct_tsk_exit(struct task_struct *tsk)
  54 {
  55         struct task_delay_info *delays = tsk->delays;
  56         spin_lock(&tsk->delays_lock);
  57         tsk->delays = NULL;
  58         spin_unlock(&tsk->delays_lock);
  59         kmem_cache_free(delayacct_cache, delays);
  60 }
  61
  62 /*
  63  * Start accounting for a delay statistic using
  64  * its starting timestamp (@start)
  65  */
  66
  67 static inline void delayacct_start(struct timespec *start)
  68 {
  69         do_posix_clock_monotonic_gettime(start);
  70 }
  71
  72 /*
  73  * Finish delay accounting for a statistic using
  74  * its timestamps (@start, @end), accumalator (@total) and @count
  75  */
  76
  77 static void delayacct_end(struct timespec *start, struct timespec *end,
  78                                 u64 *total, u32 *count)
  79 {
  80         struct timespec ts;
  81         s64 ns;
  82
  83         do_posix_clock_monotonic_gettime(end);
  84         ts = timespec_sub(*end, *start);
  85         ns = timespec_to_ns(&ts);
  86         if (ns < 0)
  87                 return;
  88
  89         spin_lock(&current->delays->lock);
  90         *total += ns;
  91         (*count)++;
  92         spin_unlock(&current->delays->lock);
  93 }
  94
  95 void __delayacct_blkio_start(void)
  96 {
  97         delayacct_start(&current->delays->blkio_start);
  98 }
  99
 100 void __delayacct_blkio_end(void)
 101 {
 102         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
 103                 /* Swapin block I/O */
 104                 delayacct_end(&current->delays->blkio_start,
 105                         &current->delays->blkio_end,
 106                         &current->delays->swapin_delay,
 107                         &current->delays->swapin_count);
 108         else    /* Other block I/O */
 109                 delayacct_end(&current->delays->blkio_start,
 110                         &current->delays->blkio_end,
 111                         &current->delays->blkio_delay,
 112                         &current->delays->blkio_count);
 113 }
 114
 115 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 116 {
 117         s64 tmp;
 118         struct timespec ts;
 119         unsigned long t1,t2,t3;
 120
 121         spin_lock(&tsk->delays_lock);
 122
 123         /* Though tsk->delays accessed later, early exit avoids
 124          * unnecessary returning of other data
 125          */
 126         if (!tsk->delays)
 127                 goto done;
 128
 129         tmp = (s64)d->cpu_run_real_total;
 130         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
 131         tmp += timespec_to_ns(&ts);
 132         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 133
 134         /*
 135          * No locking available for sched_info (and too expensive to add one)
 136          * Mitigate by taking snapshot of values
 137          */
 138         t1 = tsk->sched_info.pcnt;
 139         t2 = tsk->sched_info.run_delay;
 140         t3 = tsk->sched_info.cpu_time;
 141
 142         d->cpu_count += t1;
 143
 144         jiffies_to_timespec(t2, &ts);
 145         tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
 146         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 147
 148         tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
 149         d->cpu_run_virtual_total =
 150                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 151
 152         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 153
 154         spin_lock(&tsk->delays->lock);
 155         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 156         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 157         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 158         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 159         d->blkio_count += tsk->delays->blkio_count;
 160         d->swapin_count += tsk->delays->swapin_count;
 161         spin_unlock(&tsk->delays->lock);
 162
 163 done:
 164         spin_unlock(&tsk->delays_lock);
 165         return 0;
 166 }
 167
 168 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 169 {
 170         __u64 ret;
 171
 172         spin_lock(&tsk->delays->lock);
 173         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 174                                 tsk->delays->swapin_delay);
 175         spin_unlock(&tsk->delays->lock);
 176         return ret;
 177 }
 178