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 #include <linux/module.h>
  23
  24 int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  25 EXPORT_SYMBOL_GPL(delayacct_on);
  26 struct kmem_cache *delayacct_cache;
  27
  28 static int __init delayacct_setup_disable(char *str)
  29 {
  30         delayacct_on = 0;
  31         return 1;
  32 }
  33 __setup("nodelayacct", delayacct_setup_disable);
  34
  35 void delayacct_init(void)
  36 {
  37         delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC);
  38         delayacct_tsk_init(&init_task);
  39 }
  40
  41 void __delayacct_tsk_init(struct task_struct *tsk)
  42 {
  43         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  44         if (tsk->delays)
  45                 spin_lock_init(&tsk->delays->lock);
  46 }
  47
  48 /*
  49  * Start accounting for a delay statistic using
  50  * its starting timestamp (@start)
  51  */
  52
  53 static inline void delayacct_start(struct timespec *start)
  54 {
  55         do_posix_clock_monotonic_gettime(start);
  56 }
  57
  58 /*
  59  * Finish delay accounting for a statistic using
  60  * its timestamps (@start, @end), accumalator (@total) and @count
  61  */
  62
  63 static void delayacct_end(struct timespec *start, struct timespec *end,
  64                                 u64 *total, u32 *count)
  65 {
  66         struct timespec ts;
  67         s64 ns;
  68         unsigned long flags;
  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_irqsave(&current->delays->lock, flags);
  77         *total += ns;
  78         (*count)++;
  79         spin_unlock_irqrestore(&current->delays->lock, flags);
  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         unsigned long t1;
 106         unsigned long long t2, t3;
 107         unsigned long flags;
 108         struct timespec ts;
 109         cputime_t utime, stime, stimescaled, utimescaled;
 110
 111         /* Though tsk->delays accessed later, early exit avoids
 112          * unnecessary returning of other data
 113          */
 114         if (!tsk->delays)
 115                 goto done;
 116
 117         tmp = (s64)d->cpu_run_real_total;
 118         task_cputime(tsk, &utime, &stime);
 119         cputime_to_timespec(utime + stime, &ts);
 120         tmp += timespec_to_ns(&ts);
 121         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 122
 123         tmp = (s64)d->cpu_scaled_run_real_total;
 124         task_cputime_scaled(tsk, &utimescaled, &stimescaled);
 125         cputime_to_timespec(utimescaled + stimescaled, &ts);
 126         tmp += timespec_to_ns(&ts);
 127         d->cpu_scaled_run_real_total =
 128                 (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 129
 130         /*
 131          * No locking available for sched_info (and too expensive to add one)
 132          * Mitigate by taking snapshot of values
 133          */
 134         t1 = tsk->sched_info.pcount;
 135         t2 = tsk->sched_info.run_delay;
 136         t3 = tsk->se.sum_exec_runtime;
 137
 138         d->cpu_count += t1;
 139
 140         tmp = (s64)d->cpu_delay_total + t2;
 141         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 142
 143         tmp = (s64)d->cpu_run_virtual_total + t3;
 144         d->cpu_run_virtual_total =
 145                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 146
 147         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 148
 149         spin_lock_irqsave(&tsk->delays->lock, flags);
 150         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 151         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 152         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 153         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 154         tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 155         d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 156         d->blkio_count += tsk->delays->blkio_count;
 157         d->swapin_count += tsk->delays->swapin_count;
 158         d->freepages_count += tsk->delays->freepages_count;
 159         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 160
 161 done:
 162         return 0;
 163 }
 164
 165 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 166 {
 167         __u64 ret;
 168         unsigned long flags;
 169
 170         spin_lock_irqsave(&tsk->delays->lock, flags);
 171         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 172                                 tsk->delays->swapin_delay);
 173         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 174         return ret;
 175 }
 176
 177 void __delayacct_freepages_start(void)
 178 {
 179         delayacct_start(&current->delays->freepages_start);
 180 }
 181
 182 void __delayacct_freepages_end(void)
 183 {
 184         delayacct_end(&current->delays->freepages_start,
 185                         &current->delays->freepages_end,
 186                         &current->delays->freepages_delay,
 187                         &current->delays->freepages_count);
 188 }
 189