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 struct kmem_cache *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(task_delay_info, SLAB_PANIC);
  35         delayacct_tsk_init(&init_task);
  36 }
  37
  38 void __delayacct_tsk_init(struct task_struct *tsk)
  39 {
  40         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  41         if (tsk->delays)
  42                 spin_lock_init(&tsk->delays->lock);
  43 }
  44
  45 /*
  46  * Start accounting for a delay statistic using
  47  * its starting timestamp (@start)
  48  */
  49
  50 static inline void delayacct_start(struct timespec *start)
  51 {
  52         do_posix_clock_monotonic_gettime(start);
  53 }
  54
  55 /*
  56  * Finish delay accounting for a statistic using
  57  * its timestamps (@start, @end), accumalator (@total) and @count
  58  */
  59
  60 static void delayacct_end(struct timespec *start, struct timespec *end,
  61                                 u64 *total, u32 *count)
  62 {
  63         struct timespec ts;
  64         s64 ns;
  65         unsigned long flags;
  66
  67         do_posix_clock_monotonic_gettime(end);
  68         ts = timespec_sub(*end, *start);
  69         ns = timespec_to_ns(&ts);
  70         if (ns < 0)
  71                 return;
  72
  73         spin_lock_irqsave(&current->delays->lock, flags);
  74         *total += ns;
  75         (*count)++;
  76         spin_unlock_irqrestore(&current->delays->lock, flags);
  77 }
  78
  79 void __delayacct_blkio_start(void)
  80 {
  81         delayacct_start(&current->delays->blkio_start);
  82 }
  83
  84 void __delayacct_blkio_end(void)
  85 {
  86         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  87                 /* Swapin block I/O */
  88                 delayacct_end(&current->delays->blkio_start,
  89                         &current->delays->blkio_end,
  90                         &current->delays->swapin_delay,
  91                         &current->delays->swapin_count);
  92         else    /* Other block I/O */
  93                 delayacct_end(&current->delays->blkio_start,
  94                         &current->delays->blkio_end,
  95                         &current->delays->blkio_delay,
  96                         &current->delays->blkio_count);
  97 }
  98
  99 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 100 {
 101         s64 tmp;
 102         unsigned long t1;
 103         unsigned long long t2, t3;
 104         unsigned long flags;
 105         struct timespec ts;
 106
 107         /* Though tsk->delays accessed later, early exit avoids
 108          * unnecessary returning of other data
 109          */
 110         if (!tsk->delays)
 111                 goto done;
 112
 113         tmp = (s64)d->cpu_run_real_total;
 114         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
 115         tmp += timespec_to_ns(&ts);
 116         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 117
 118         /*
 119          * No locking available for sched_info (and too expensive to add one)
 120          * Mitigate by taking snapshot of values
 121          */
 122         t1 = tsk->sched_info.pcount;
 123         t2 = tsk->sched_info.run_delay;
 124         t3 = tsk->sched_info.cpu_time;
 125
 126         d->cpu_count += t1;
 127
 128         tmp = (s64)d->cpu_delay_total + t2;
 129         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 130
 131         tmp = (s64)d->cpu_run_virtual_total + t3;
 132         d->cpu_run_virtual_total =
 133                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 134
 135         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 136
 137         spin_lock_irqsave(&tsk->delays->lock, flags);
 138         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 139         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 140         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 141         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 142         d->blkio_count += tsk->delays->blkio_count;
 143         d->swapin_count += tsk->delays->swapin_count;
 144         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 145
 146 done:
 147         return 0;
 148 }
 149
 150 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 151 {
 152         __u64 ret;
 153         unsigned long flags;
 154
 155         spin_lock_irqsave(&tsk->delays->lock, flags);
 156         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 157                                 tsk->delays->swapin_delay);
 158         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 159         return ret;
 160 }
 161