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_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, GFP_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         unsigned long flags;
  70
  71         do_posix_clock_monotonic_gettime(end);
  72         ts = timespec_sub(*end, *start);
  73         ns = timespec_to_ns(&ts);
  74         if (ns < 0)
  75                 return;
  76
  77         spin_lock_irqsave(&current->delays->lock, flags);
  78         *total += ns;
  79         (*count)++;
  80         spin_unlock_irqrestore(&current->delays->lock, flags);
  81 }
  82
  83 void __delayacct_blkio_start(void)
  84 {
  85         delayacct_start(&current->delays->blkio_start);
  86 }
  87
  88 void __delayacct_blkio_end(void)
  89 {
  90         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  91                 /* Swapin block I/O */
  92                 delayacct_end(&current->delays->blkio_start,
  93                         &current->delays->blkio_end,
  94                         &current->delays->swapin_delay,
  95                         &current->delays->swapin_count);
  96         else    /* Other block I/O */
  97                 delayacct_end(&current->delays->blkio_start,
  98                         &current->delays->blkio_end,
  99                         &current->delays->blkio_delay,
 100                         &current->delays->blkio_count);
 101 }
 102
 103 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 104 {
 105         s64 tmp;
 106         struct timespec ts;
 107         unsigned long t1,t2,t3;
 108         unsigned long flags;
 109
 110         /* Though tsk->delays accessed later, early exit avoids
 111          * unnecessary returning of other data
 112          */
 113         if (!tsk->delays)
 114                 goto done;
 115
 116         tmp = (s64)d->cpu_run_real_total;
 117         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
 118         tmp += timespec_to_ns(&ts);
 119         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 120
 121         /*
 122          * No locking available for sched_info (and too expensive to add one)
 123          * Mitigate by taking snapshot of values
 124          */
 125         t1 = tsk->sched_info.pcnt;
 126         t2 = tsk->sched_info.run_delay;
 127         t3 = tsk->sched_info.cpu_time;
 128
 129         d->cpu_count += t1;
 130
 131         jiffies_to_timespec(t2, &ts);
 132         tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
 133         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 134
 135         tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
 136         d->cpu_run_virtual_total =
 137                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 138
 139         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 140
 141         spin_lock_irqsave(&tsk->delays->lock, flags);
 142         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 143         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 144         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 145         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 146         d->blkio_count += tsk->delays->blkio_count;
 147         d->swapin_count += tsk->delays->swapin_count;
 148         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 149
 150 done:
 151         return 0;
 152 }
 153
 154 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 155 {
 156         __u64 ret;
 157         unsigned long flags;
 158
 159         spin_lock_irqsave(&tsk->delays->lock, flags);
 160         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 161                                 tsk->delays->swapin_delay);
 162         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 163         return ret;
 164 }
 165