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/sched/task.h>
  18 #include <linux/sched/cputime.h>
  19 #include <linux/slab.h>
  20 #include <linux/taskstats.h>
  21 #include <linux/time.h>
  22 #include <linux/sysctl.h>
  23 #include <linux/delayacct.h>
  24 #include <linux/module.h>
  25
  26 int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  27 EXPORT_SYMBOL_GPL(delayacct_on);
  28 struct kmem_cache *delayacct_cache;
  29
  30 static int __init delayacct_setup_disable(char *str)
  31 {
  32         delayacct_on = 0;
  33         return 1;
  34 }
  35 __setup("nodelayacct", delayacct_setup_disable);
  36
  37 void delayacct_init(void)
  38 {
  39         delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
  40         delayacct_tsk_init(&init_task);
  41 }
  42
  43 void __delayacct_tsk_init(struct task_struct *tsk)
  44 {
  45         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  46         if (tsk->delays)
  47                 raw_spin_lock_init(&tsk->delays->lock);
  48 }
  49
  50 /*
  51  * Finish delay accounting for a statistic using its timestamps (@start),
  52  * accumalator (@total) and @count
  53  */
  54 static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total,
  55                           u32 *count)
  56 {
  57         s64 ns = ktime_get_ns() - *start;
  58         unsigned long flags;
  59
  60         if (ns > 0) {
  61                 raw_spin_lock_irqsave(lock, flags);
  62                 *total += ns;
  63                 (*count)++;
  64                 raw_spin_unlock_irqrestore(lock, flags);
  65         }
  66 }
  67
  68 void __delayacct_blkio_start(void)
  69 {
  70         current->delays->blkio_start = ktime_get_ns();
  71 }
  72
  73 /*
  74  * We cannot rely on the `current` macro, as we haven't yet switched back to
  75  * the process being woken.
  76  */
  77 void __delayacct_blkio_end(struct task_struct *p)
  78 {
  79         struct task_delay_info *delays = p->delays;
  80         u64 *total;
  81         u32 *count;
  82
  83         if (p->delays->flags & DELAYACCT_PF_SWAPIN) {
  84                 total = &delays->swapin_delay;
  85                 count = &delays->swapin_count;
  86         } else {
  87                 total = &delays->blkio_delay;
  88                 count = &delays->blkio_count;
  89         }
  90
  91         delayacct_end(&delays->lock, &delays->blkio_start, total, count);
  92 }
  93
  94 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
  95 {
  96         u64 utime, stime, stimescaled, utimescaled;
  97         unsigned long long t2, t3;
  98         unsigned long flags, t1;
  99         s64 tmp;
 100
 101         task_cputime(tsk, &utime, &stime);
 102         tmp = (s64)d->cpu_run_real_total;
 103         tmp += utime + stime;
 104         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 105
 106         task_cputime_scaled(tsk, &utimescaled, &stimescaled);
 107         tmp = (s64)d->cpu_scaled_run_real_total;
 108         tmp += utimescaled + stimescaled;
 109         d->cpu_scaled_run_real_total =
 110                 (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 111
 112         /*
 113          * No locking available for sched_info (and too expensive to add one)
 114          * Mitigate by taking snapshot of values
 115          */
 116         t1 = tsk->sched_info.pcount;
 117         t2 = tsk->sched_info.run_delay;
 118         t3 = tsk->se.sum_exec_runtime;
 119
 120         d->cpu_count += t1;
 121
 122         tmp = (s64)d->cpu_delay_total + t2;
 123         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 124
 125         tmp = (s64)d->cpu_run_virtual_total + t3;
 126         d->cpu_run_virtual_total =
 127                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 128
 129         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 130
 131         raw_spin_lock_irqsave(&tsk->delays->lock, flags);
 132         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 133         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 134         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 135         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 136         tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 137         d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 138         d->blkio_count += tsk->delays->blkio_count;
 139         d->swapin_count += tsk->delays->swapin_count;
 140         d->freepages_count += tsk->delays->freepages_count;
 141         raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 142
 143         return 0;
 144 }
 145
 146 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 147 {
 148         __u64 ret;
 149         unsigned long flags;
 150
 151         raw_spin_lock_irqsave(&tsk->delays->lock, flags);
 152         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 153                                 tsk->delays->swapin_delay);
 154         raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 155         return ret;
 156 }
 157
 158 void __delayacct_freepages_start(void)
 159 {
 160         current->delays->freepages_start = ktime_get_ns();
 161 }
 162
 163 void __delayacct_freepages_end(void)
 164 {
 165         delayacct_end(
 166                 &current->delays->lock,
 167                 &current->delays->freepages_start,
 168                 &current->delays->freepages_delay,
 169                 &current->delays->freepages_count);
 170 }
 171