Root/kernel/delayacct.c

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
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    tmp = (s64)d->cpu_scaled_run_real_total;
122    cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
123    tmp += timespec_to_ns(&ts);
124    d->cpu_scaled_run_real_total =
125        (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
126
127    /*
128     * No locking available for sched_info (and too expensive to add one)
129     * Mitigate by taking snapshot of values
130     */
131    t1 = tsk->sched_info.pcount;
132    t2 = tsk->sched_info.run_delay;
133    t3 = tsk->se.sum_exec_runtime;
134
135    d->cpu_count += t1;
136
137    tmp = (s64)d->cpu_delay_total + t2;
138    d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
139
140    tmp = (s64)d->cpu_run_virtual_total + t3;
141    d->cpu_run_virtual_total =
142        (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
143
144    /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
145
146    spin_lock_irqsave(&tsk->delays->lock, flags);
147    tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
148    d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
149    tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
150    d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
151    tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
152    d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
153    d->blkio_count += tsk->delays->blkio_count;
154    d->swapin_count += tsk->delays->swapin_count;
155    d->freepages_count += tsk->delays->freepages_count;
156    spin_unlock_irqrestore(&tsk->delays->lock, flags);
157
158done:
159    return 0;
160}
161
162__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
163{
164    __u64 ret;
165    unsigned long flags;
166
167    spin_lock_irqsave(&tsk->delays->lock, flags);
168    ret = nsec_to_clock_t(tsk->delays->blkio_delay +
169                tsk->delays->swapin_delay);
170    spin_unlock_irqrestore(&tsk->delays->lock, flags);
171    return ret;
172}
173
174void __delayacct_freepages_start(void)
175{
176    delayacct_start(&current->delays->freepages_start);
177}
178
179void __delayacct_freepages_end(void)
180{
181    delayacct_end(&current->delays->freepages_start,
182            &current->delays->freepages_end,
183            &current->delays->freepages_delay,
184            &current->delays->freepages_count);
185}
186
187

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