[PATCH] task delay accounting fixes
[linux-2.6.git] / 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/time.h>
19 #include <linux/sysctl.h>
20 #include <linux/delayacct.h>
21
22 int delayacct_on __read_mostly = 1;     /* Delay accounting turned on/off */
23 kmem_cache_t *delayacct_cache;
24
25 static int __init delayacct_setup_disable(char *str)
26 {
27         delayacct_on = 0;
28         return 1;
29 }
30 __setup("nodelayacct", delayacct_setup_disable);
31
32 void 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
42 void __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
54 static 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
64 static void delayacct_end(struct timespec *start, struct timespec *end,
65                                 u64 *total, u32 *count)
66 {
67         struct timespec ts;
68         s64 ns;
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(&current->delays->lock);
77         *total += ns;
78         (*count)++;
79         spin_unlock(&current->delays->lock);
80 }
81
82 void __delayacct_blkio_start(void)
83 {
84         delayacct_start(&current->delays->blkio_start);
85 }
86
87 void __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
102 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
103 {
104         s64 tmp;
105         struct timespec ts;
106         unsigned long t1,t2,t3;
107
108         /* Though tsk->delays accessed later, early exit avoids
109          * unnecessary returning of other data
110          */
111         if (!tsk->delays)
112                 goto done;
113
114         tmp = (s64)d->cpu_run_real_total;
115         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
116         tmp += timespec_to_ns(&ts);
117         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
118
119         /*
120          * No locking available for sched_info (and too expensive to add one)
121          * Mitigate by taking snapshot of values
122          */
123         t1 = tsk->sched_info.pcnt;
124         t2 = tsk->sched_info.run_delay;
125         t3 = tsk->sched_info.cpu_time;
126
127         d->cpu_count += t1;
128
129         jiffies_to_timespec(t2, &ts);
130         tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
131         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
132
133         tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
134         d->cpu_run_virtual_total =
135                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
136
137         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
138
139         spin_lock(&tsk->delays->lock);
140         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
141         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
142         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
143         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
144         d->blkio_count += tsk->delays->blkio_count;
145         d->swapin_count += tsk->delays->swapin_count;
146         spin_unlock(&tsk->delays->lock);
147
148 done:
149         return 0;
150 }
151
152 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
153 {
154         __u64 ret;
155
156         spin_lock(&tsk->delays->lock);
157         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
158                                 tsk->delays->swapin_delay);
159         spin_unlock(&tsk->delays->lock);
160         return ret;
161 }
162