/* 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;
        cputime_t utime, stime, stimescaled, utimescaled;

        /* 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;
        task_cputime(tsk, &utime, &stime);
        cputime_to_timespec(utime + 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;
        task_cputime_scaled(tsk, &utimescaled, &stimescaled);
        cputime_to_timespec(utimescaled + 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);
}