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