delayacct.c

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/* delayacct.c - per-task delay accounting
 *
 * Copyright (C) Shailabh Nagar, IBM Corp. 2006
 *
 * This program is free software;  you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
 * the GNU General Public License for more details.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/taskstats.h>
#include <linux/time.h>
#include <linux/sysctl.h>
#include <linux/delayacct.h>
#include <linux/module.h>

int delayacct_on __read_mostly = 1; /* Delay accounting turned on/off */
EXPORT_SYMBOL_GPL(delayacct_on);
struct kmem_cache *delayacct_cache;

static int __init delayacct_setup_disable(char *str)
{
    delayacct_on = 0;
    return 1;
}
__setup("nodelayacct", delayacct_setup_disable);

void delayacct_init(void)
{
    delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC);
    delayacct_tsk_init(&init_task);
}

void __delayacct_tsk_init(struct task_struct *tsk)
{
    tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
    if (tsk->delays)
        spin_lock_init(&tsk->delays->lock);
}

/*
 * Start accounting for a delay statistic using
 * its starting timestamp (@start)
 */

static inline void delayacct_start(struct timespec *start)
{
    do_posix_clock_monotonic_gettime(start);
}

/*
 * Finish delay accounting for a statistic using
 * its timestamps (@start, @end), accumalator (@total) and @count
 */

static void delayacct_end(struct timespec *start, struct timespec *end,
                u64 *total, u32 *count)
{
    struct timespec ts;
    s64 ns;
    unsigned long flags;

    do_posix_clock_monotonic_gettime(end);
    ts = timespec_sub(*end, *start);
    ns = timespec_to_ns(&ts);
    if (ns < 0)
        return;

    spin_lock_irqsave(&current->delays->lock, flags);
    *total += ns;
    (*count)++;
    spin_unlock_irqrestore(&current->delays->lock, flags);
}

void __delayacct_blkio_start(void)
{
    delayacct_start(&current->delays->blkio_start);
}

void __delayacct_blkio_end(void)
{
    if (current->delays->flags & DELAYACCT_PF_SWAPIN)
        /* Swapin block I/O */
        delayacct_end(&current->delays->blkio_start,
            &current->delays->blkio_end,
            &current->delays->swapin_delay,
            &current->delays->swapin_count);
    else    /* Other block I/O */
        delayacct_end(&current->delays->blkio_start,
            &current->delays->blkio_end,
            &current->delays->blkio_delay,
            &current->delays->blkio_count);
}

int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
{
    s64 tmp;
    unsigned long t1;
    unsigned long long t2, t3;
    unsigned long flags;
    struct timespec ts;

    /* Though tsk->delays accessed later, early exit avoids
     * unnecessary returning of other data
     */
    if (!tsk->delays)
        goto done;

    tmp = (s64)d->cpu_run_real_total;
    cputime_to_timespec(tsk->utime + tsk->stime, &ts);
    tmp += timespec_to_ns(&ts);
    d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;

    tmp = (s64)d->cpu_scaled_run_real_total;
    cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
    tmp += timespec_to_ns(&ts);
    d->cpu_scaled_run_real_total =
        (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;

    /*
     * No locking available for sched_info (and too expensive to add one)
     * Mitigate by taking snapshot of values
     */
    t1 = tsk->sched_info.pcount;
    t2 = tsk->sched_info.run_delay;
    t3 = tsk->se.sum_exec_runtime;

    d->cpu_count += t1;

    tmp = (s64)d->cpu_delay_total + t2;
    d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;

    tmp = (s64)d->cpu_run_virtual_total + t3;
    d->cpu_run_virtual_total =
        (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;

    /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */

    spin_lock_irqsave(&tsk->delays->lock, flags);
    tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
    d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
    tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
    d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
    tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
    d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
    d->blkio_count += tsk->delays->blkio_count;
    d->swapin_count += tsk->delays->swapin_count;
    d->freepages_count += tsk->delays->freepages_count;
    spin_unlock_irqrestore(&tsk->delays->lock, flags);

done:
    return 0;
}

__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
{
    __u64 ret;
    unsigned long flags;

    spin_lock_irqsave(&tsk->delays->lock, flags);
    ret = nsec_to_clock_t(tsk->delays->blkio_delay +
                tsk->delays->swapin_delay);
    spin_unlock_irqrestore(&tsk->delays->lock, flags);
    return ret;
}

void __delayacct_freepages_start(void)
{
    delayacct_start(&current->delays->freepages_start);
}

void __delayacct_freepages_end(void)
{
    delayacct_end(&current->delays->freepages_start,
            &current->delays->freepages_end,
            &current->delays->freepages_delay,
            &current->delays->freepages_count);
}