linux/kernel/delayacct.c
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   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/time.h>
  19#include <linux/sysctl.h>
  20#include <linux/delayacct.h>
  21
  22int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  23struct kmem_cache *delayacct_cache;
  24
  25static int __init delayacct_setup_disable(char *str)
  26{
  27        delayacct_on = 0;
  28        return 1;
  29}
  30__setup("nodelayacct", delayacct_setup_disable);
  31
  32void delayacct_init(void)
  33{
  34        delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC);
  35        delayacct_tsk_init(&init_task);
  36}
  37
  38void __delayacct_tsk_init(struct task_struct *tsk)
  39{
  40        tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  41        if (tsk->delays)
  42                spin_lock_init(&tsk->delays->lock);
  43}
  44
  45/*
  46 * Start accounting for a delay statistic using
  47 * its starting timestamp (@start)
  48 */
  49
  50static inline void delayacct_start(struct timespec *start)
  51{
  52        do_posix_clock_monotonic_gettime(start);
  53}
  54
  55/*
  56 * Finish delay accounting for a statistic using
  57 * its timestamps (@start, @end), accumalator (@total) and @count
  58 */
  59
  60static void delayacct_end(struct timespec *start, struct timespec *end,
  61                                u64 *total, u32 *count)
  62{
  63        struct timespec ts;
  64        s64 ns;
  65        unsigned long flags;
  66
  67        do_posix_clock_monotonic_gettime(end);
  68        ts = timespec_sub(*end, *start);
  69        ns = timespec_to_ns(&ts);
  70        if (ns < 0)
  71                return;
  72
  73        spin_lock_irqsave(&current->delays->lock, flags);
  74        *total += ns;
  75        (*count)++;
  76        spin_unlock_irqrestore(&current->delays->lock, flags);
  77}
  78
  79void __delayacct_blkio_start(void)
  80{
  81        delayacct_start(&current->delays->blkio_start);
  82}
  83
  84void __delayacct_blkio_end(void)
  85{
  86        if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  87                /* Swapin block I/O */
  88                delayacct_end(&current->delays->blkio_start,
  89                        &current->delays->blkio_end,
  90                        &current->delays->swapin_delay,
  91                        &current->delays->swapin_count);
  92        else    /* Other block I/O */
  93                delayacct_end(&current->delays->blkio_start,
  94                        &current->delays->blkio_end,
  95                        &current->delays->blkio_delay,
  96                        &current->delays->blkio_count);
  97}
  98
  99int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 100{
 101        s64 tmp;
 102        unsigned long t1;
 103        unsigned long long t2, t3;
 104        unsigned long flags;
 105        struct timespec ts;
 106
 107        /* Though tsk->delays accessed later, early exit avoids
 108         * unnecessary returning of other data
 109         */
 110        if (!tsk->delays)
 111                goto done;
 112
 113        tmp = (s64)d->cpu_run_real_total;
 114        cputime_to_timespec(tsk->utime + tsk->stime, &ts);
 115        tmp += timespec_to_ns(&ts);
 116        d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 117
 118        tmp = (s64)d->cpu_scaled_run_real_total;
 119        cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
 120        tmp += timespec_to_ns(&ts);
 121        d->cpu_scaled_run_real_total =
 122                (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 123
 124        /*
 125         * No locking available for sched_info (and too expensive to add one)
 126         * Mitigate by taking snapshot of values
 127         */
 128        t1 = tsk->sched_info.pcount;
 129        t2 = tsk->sched_info.run_delay;
 130        t3 = tsk->se.sum_exec_runtime;
 131
 132        d->cpu_count += t1;
 133
 134        tmp = (s64)d->cpu_delay_total + t2;
 135        d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 136
 137        tmp = (s64)d->cpu_run_virtual_total + t3;
 138        d->cpu_run_virtual_total =
 139                (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 140
 141        /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 142
 143        spin_lock_irqsave(&tsk->delays->lock, flags);
 144        tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 145        d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 146        tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 147        d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 148        tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 149        d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 150        d->blkio_count += tsk->delays->blkio_count;
 151        d->swapin_count += tsk->delays->swapin_count;
 152        d->freepages_count += tsk->delays->freepages_count;
 153        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 154
 155done:
 156        return 0;
 157}
 158
 159__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 160{
 161        __u64 ret;
 162        unsigned long flags;
 163
 164        spin_lock_irqsave(&tsk->delays->lock, flags);
 165        ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 166                                tsk->delays->swapin_delay);
 167        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 168        return ret;
 169}
 170
 171void __delayacct_freepages_start(void)
 172{
 173        delayacct_start(&current->delays->freepages_start);
 174}
 175
 176void __delayacct_freepages_end(void)
 177{
 178        delayacct_end(&current->delays->freepages_start,
 179                        &current->delays->freepages_end,
 180                        &current->delays->freepages_delay,
 181                        &current->delays->freepages_count);
 182}
 183
 184