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/taskstats.h>
  19#include <linux/time.h>
  20#include <linux/sysctl.h>
  21#include <linux/delayacct.h>
  22#include <linux/module.h>
  23
  24int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
  25EXPORT_SYMBOL_GPL(delayacct_on);
  26struct kmem_cache *delayacct_cache;
  27
  28static int __init delayacct_setup_disable(char *str)
  29{
  30        delayacct_on = 0;
  31        return 1;
  32}
  33__setup("nodelayacct", delayacct_setup_disable);
  34
  35void delayacct_init(void)
  36{
  37        delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC);
  38        delayacct_tsk_init(&init_task);
  39}
  40
  41void __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
  53static 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
  63static 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
  82void __delayacct_blkio_start(void)
  83{
  84        delayacct_start(&current->delays->blkio_start);
  85}
  86
  87void __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
 102int __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        cputime_t utime, stime, stimescaled, utimescaled;
 110
 111        /* Though tsk->delays accessed later, early exit avoids
 112         * unnecessary returning of other data
 113         */
 114        if (!tsk->delays)
 115                goto done;
 116
 117        tmp = (s64)d->cpu_run_real_total;
 118        task_cputime(tsk, &utime, &stime);
 119        cputime_to_timespec(utime + stime, &ts);
 120        tmp += timespec_to_ns(&ts);
 121        d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 122
 123        tmp = (s64)d->cpu_scaled_run_real_total;
 124        task_cputime_scaled(tsk, &utimescaled, &stimescaled);
 125        cputime_to_timespec(utimescaled + stimescaled, &ts);
 126        tmp += timespec_to_ns(&ts);
 127        d->cpu_scaled_run_real_total =
 128                (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 129
 130        /*
 131         * No locking available for sched_info (and too expensive to add one)
 132         * Mitigate by taking snapshot of values
 133         */
 134        t1 = tsk->sched_info.pcount;
 135        t2 = tsk->sched_info.run_delay;
 136        t3 = tsk->se.sum_exec_runtime;
 137
 138        d->cpu_count += t1;
 139
 140        tmp = (s64)d->cpu_delay_total + t2;
 141        d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 142
 143        tmp = (s64)d->cpu_run_virtual_total + t3;
 144        d->cpu_run_virtual_total =
 145                (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 146
 147        /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 148
 149        spin_lock_irqsave(&tsk->delays->lock, flags);
 150        tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 151        d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 152        tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 153        d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 154        tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 155        d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 156        d->blkio_count += tsk->delays->blkio_count;
 157        d->swapin_count += tsk->delays->swapin_count;
 158        d->freepages_count += tsk->delays->freepages_count;
 159        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 160
 161done:
 162        return 0;
 163}
 164
 165__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 166{
 167        __u64 ret;
 168        unsigned long flags;
 169
 170        spin_lock_irqsave(&tsk->delays->lock, flags);
 171        ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 172                                tsk->delays->swapin_delay);
 173        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 174        return ret;
 175}
 176
 177void __delayacct_freepages_start(void)
 178{
 179        delayacct_start(&current->delays->freepages_start);
 180}
 181
 182void __delayacct_freepages_end(void)
 183{
 184        delayacct_end(&current->delays->freepages_start,
 185                        &current->delays->freepages_end,
 186                        &current->delays->freepages_delay,
 187                        &current->delays->freepages_count);
 188}
 189
 190
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