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
 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         tmp = (s64)d->cpu_scaled_run_real_total;
 122         cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
 123         tmp += timespec_to_ns(&ts);
 124         d->cpu_scaled_run_real_total =
 125                 (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 126
 127         /*
 128          * No locking available for sched_info (and too expensive to add one)
 129          * Mitigate by taking snapshot of values
 130          */
 131         t1 = tsk->sched_info.pcount;
 132         t2 = tsk->sched_info.run_delay;
 133         t3 = tsk->se.sum_exec_runtime;
 134
 135         d->cpu_count += t1;
 136
 137         tmp = (s64)d->cpu_delay_total + t2;
 138         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 139
 140         tmp = (s64)d->cpu_run_virtual_total + t3;
 141         d->cpu_run_virtual_total =
 142                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 143
 144         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 145
 146         spin_lock_irqsave(&tsk->delays->lock, flags);
 147         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 148         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 149         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 150         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 151         tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 152         d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 153         d->blkio_count += tsk->delays->blkio_count;
 154         d->swapin_count += tsk->delays->swapin_count;
 155         d->freepages_count += tsk->delays->freepages_count;
 156         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 157
 158 done:
 159         return 0;
 160 }
 161
 162 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 163 {
 164         __u64 ret;
 165         unsigned long flags;
 166
 167         spin_lock_irqsave(&tsk->delays->lock, flags);
 168         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 169                                 tsk->delays->swapin_delay);
 170         spin_unlock_irqrestore(&tsk->delays->lock, flags);
 171         return ret;
 172 }
 173
 174 void __delayacct_freepages_start(void)
 175 {
 176         delayacct_start(&current->delays->freepages_start);
 177 }
 178
 179 void __delayacct_freepages_end(void)
 180 {
 181         delayacct_end(&current->delays->freepages_start,
 182                         &current->delays->freepages_end,
 183                         &current->delays->freepages_delay,
 184                         &current->delays->freepages_count);
 185 }
 186