linux/kernel/delayacct.c
<<
>>
Prefs
   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 */
  23kmem_cache_t *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_create("delayacct_cache",
  35                                        sizeof(struct task_delay_info),
  36                                        0,
  37                                        SLAB_PANIC,
  38                                        NULL, NULL);
  39        delayacct_tsk_init(&init_task);
  40}
  41
  42void __delayacct_tsk_init(struct task_struct *tsk)
  43{
  44        tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
  45        if (tsk->delays)
  46                spin_lock_init(&tsk->delays->lock);
  47}
  48
  49/*
  50 * Start accounting for a delay statistic using
  51 * its starting timestamp (@start)
  52 */
  53
  54static inline void delayacct_start(struct timespec *start)
  55{
  56        do_posix_clock_monotonic_gettime(start);
  57}
  58
  59/*
  60 * Finish delay accounting for a statistic using
  61 * its timestamps (@start, @end), accumalator (@total) and @count
  62 */
  63
  64static void delayacct_end(struct timespec *start, struct timespec *end,
  65                                u64 *total, u32 *count)
  66{
  67        struct timespec ts;
  68        s64 ns;
  69        unsigned long flags;
  70
  71        do_posix_clock_monotonic_gettime(end);
  72        ts = timespec_sub(*end, *start);
  73        ns = timespec_to_ns(&ts);
  74        if (ns < 0)
  75                return;
  76
  77        spin_lock_irqsave(&current->delays->lock, flags);
  78        *total += ns;
  79        (*count)++;
  80        spin_unlock_irqrestore(&current->delays->lock, flags);
  81}
  82
  83void __delayacct_blkio_start(void)
  84{
  85        delayacct_start(&current->delays->blkio_start);
  86}
  87
  88void __delayacct_blkio_end(void)
  89{
  90        if (current->delays->flags & DELAYACCT_PF_SWAPIN)
  91                /* Swapin block I/O */
  92                delayacct_end(&current->delays->blkio_start,
  93                        &current->delays->blkio_end,
  94                        &current->delays->swapin_delay,
  95                        &current->delays->swapin_count);
  96        else    /* Other block I/O */
  97                delayacct_end(&current->delays->blkio_start,
  98                        &current->delays->blkio_end,
  99                        &current->delays->blkio_delay,
 100                        &current->delays->blkio_count);
 101}
 102
 103int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 104{
 105        s64 tmp;
 106        struct timespec ts;
 107        unsigned long t1,t2,t3;
 108        unsigned long flags;
 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        /*
 122         * No locking available for sched_info (and too expensive to add one)
 123         * Mitigate by taking snapshot of values
 124         */
 125        t1 = tsk->sched_info.pcnt;
 126        t2 = tsk->sched_info.run_delay;
 127        t3 = tsk->sched_info.cpu_time;
 128
 129        d->cpu_count += t1;
 130
 131        jiffies_to_timespec(t2, &ts);
 132        tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
 133        d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 134
 135        tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
 136        d->cpu_run_virtual_total =
 137                (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 138
 139        /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 140
 141        spin_lock_irqsave(&tsk->delays->lock, flags);
 142        tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 143        d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 144        tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 145        d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 146        d->blkio_count += tsk->delays->blkio_count;
 147        d->swapin_count += tsk->delays->swapin_count;
 148        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 149
 150done:
 151        return 0;
 152}
 153
 154__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 155{
 156        __u64 ret;
 157        unsigned long flags;
 158
 159        spin_lock_irqsave(&tsk->delays->lock, flags);
 160        ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 161                                tsk->delays->swapin_delay);
 162        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 163        return ret;
 164}
 165
 166