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/taskstats.h>
  19 #include <linux/time.h>
  20 #include <linux/sysctl.h>
  21 #include <linux/delayacct.h>
  22
  23 int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  24 struct kmem_cache *delayacct_cache;
  25
  26 static int __init delayacct_setup_disable(char *str)
  27 {
  28         delayacct_on = 0;
  29         return 1;
  30 }
  31 __setup("nodelayacct", delayacct_setup_disable);
  32
  33 void delayacct_init(void)
  34 {
  35         delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC);
  36         delayacct_tsk_init(&init_task);
  37 }
  38
  39 void __delayacct_tsk_init(struct task_struct *tsk)
  40 {
  41         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  42         if (tsk->delays)
  43                 spin_lock_init(&tsk->delays->lock);
  44 }
  45
  46 /*
  47  * Start accounting for a delay statistic using
  48  * its starting timestamp (@start)
  49  */
  50
  51 static inline void delayacct_start(struct timespec *start)
  52 {
  53         do_posix_clock_monotonic_gettime(start);
  54 }
  55
  56 /*
  57  * Finish delay accounting for a statistic using
  58  * its timestamps (@start, @end), accumalator (@total) and @count
  59  */
  60
  61 static void delayacct_end(struct timespec *start, struct timespec *end,
  62                                 u64 *total, u32 *count)
  63 {
  64         struct timespec ts;
  65         s64 ns;
  66         unsigned long flags;
  67
  68         do_posix_clock_monotonic_gettime(end);
  69         ts = timespec_sub(*end, *start);
  70         ns = timespec_to_ns(&ts);
  71         if (ns < 0)
  72                 return;
  73
  74         spin_lock_irqsave(&current->delays->lock, flags);
  75         *total += ns;
  76         (*count)++;
  77         spin_unlock_irqrestore(&current->delays->lock, flags);
  78 }
  79
  80 void __delayacct_blkio_start(void)
  81 {
  82         delayacct_start(&current->delays->blkio_start);
  83 }
  84
  85 void __delayacct_blkio_end(void)
  86 {
  87         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  88                 /* Swapin block I/O */
  89                 delayacct_end(&current->delays->blkio_start,
  90                         &current->delays->blkio_end,
  91                         &current->delays->swapin_delay,
  92                         &current->delays->swapin_count);
  93         else    /* Other block I/O */
  94                 delayacct_end(&current->delays->blkio_start,
  95                         &current->delays->blkio_end,
  96                         &current->delays->blkio_delay,
  97                         &current->delays->blkio_count);
  98 }
  99
 100 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 101 {
 102         s64 tmp;
 103         unsigned long t1;
 104         unsigned long long t2, t3;
 105         unsigned long flags;
 106         struct timespec ts;
 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         tmp = (s64)d->cpu_scaled_run_real_total;
 120         cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
 121         tmp += timespec_to_ns(&ts);
 122         d->cpu_scaled_run_real_total =
 123                 (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 124
 125         /*
 126          * No locking available for sched_info (and too expensive to add one)
 127          * Mitigate by taking snapshot of values
 128          */
 129         t1 = tsk->sched_info.pcount;
 130         t2 = tsk->sched_info.run_delay;
 131         t3 = tsk->se.sum_exec_runtime;
 132
 133         d->cpu_count += t1;
 134
 135         tmp = (s64)d->cpu_delay_total + t2;
 136         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 137
 138         tmp = (s64)d->cpu_run_virtual_total + t3;
 139         d->cpu_run_virtual_total =
 140                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 141
 142         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 143
 144         spin_lock_irqsave(&tsk->delays->lock, flags);
 145         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 146         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 147         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 148         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 149         tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 150         d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 151         d->blkio_count += tsk->delays->blkio_count;
 152         d->swapin_count += tsk->delays->swapin_count;
 153         d->freepages_count += tsk->delays->freepages_count;
 154         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 155
 156 done:
 157         return 0;
 158 }
 159
 160 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 161 {
 162         __u64 ret;
 163         unsigned long flags;
 164
 165         spin_lock_irqsave(&tsk->delays->lock, flags);
 166         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 167                                 tsk->delays->swapin_delay);
 168         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 169         return ret;
 170 }
 171
 172 void __delayacct_freepages_start(void)
 173 {
 174         delayacct_start(&current->delays->freepages_start);
 175 }
 176
 177 void __delayacct_freepages_end(void)
 178 {
 179         delayacct_end(&current->delays->freepages_start,
 180                         &current->delays->freepages_end,
 181                         &current->delays->freepages_delay,
 182                         &current->delays->freepages_count);
 183 }
 184