[PATCH] delay accounting: temporarily enable by default
[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         spin_lock_init(&tsk->delays_lock);
45         /* No need to acquire tsk->delays_lock for allocation here unless
46            __delayacct_tsk_init called after tsk is attached to tasklist
47         */
48         tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
49         if (tsk->delays)
50                 spin_lock_init(&tsk->delays->lock);
51 }
52
53 void __delayacct_tsk_exit(struct task_struct *tsk)
54 {
55         struct task_delay_info *delays = tsk->delays;
56         spin_lock(&tsk->delays_lock);
57         tsk->delays = NULL;
58         spin_unlock(&tsk->delays_lock);
59         kmem_cache_free(delayacct_cache, delays);
60 }
61
62 /*
63  * Start accounting for a delay statistic using
64  * its starting timestamp (@start)
65  */
66
67 static inline void delayacct_start(struct timespec *start)
68 {
69         do_posix_clock_monotonic_gettime(start);
70 }
71
72 /*
73  * Finish delay accounting for a statistic using
74  * its timestamps (@start, @end), accumalator (@total) and @count
75  */
76
77 static void delayacct_end(struct timespec *start, struct timespec *end,
78                                 u64 *total, u32 *count)
79 {
80         struct timespec ts;
81         s64 ns;
82
83         do_posix_clock_monotonic_gettime(end);
84         ts = timespec_sub(*end, *start);
85         ns = timespec_to_ns(&ts);
86         if (ns < 0)
87                 return;
88
89         spin_lock(&current->delays->lock);
90         *total += ns;
91         (*count)++;
92         spin_unlock(&current->delays->lock);
93 }
94
95 void __delayacct_blkio_start(void)
96 {
97         delayacct_start(&current->delays->blkio_start);
98 }
99
100 void __delayacct_blkio_end(void)
101 {
102         if (current->delays->flags & DELAYACCT_PF_SWAPIN)
103                 /* Swapin block I/O */
104                 delayacct_end(&current->delays->blkio_start,
105                         &current->delays->blkio_end,
106                         &current->delays->swapin_delay,
107                         &current->delays->swapin_count);
108         else    /* Other block I/O */
109                 delayacct_end(&current->delays->blkio_start,
110                         &current->delays->blkio_end,
111                         &current->delays->blkio_delay,
112                         &current->delays->blkio_count);
113 }
114
115 int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
116 {
117         s64 tmp;
118         struct timespec ts;
119         unsigned long t1,t2,t3;
120
121         spin_lock(&tsk->delays_lock);
122
123         /* Though tsk->delays accessed later, early exit avoids
124          * unnecessary returning of other data
125          */
126         if (!tsk->delays)
127                 goto done;
128
129         tmp = (s64)d->cpu_run_real_total;
130         cputime_to_timespec(tsk->utime + tsk->stime, &ts);
131         tmp += timespec_to_ns(&ts);
132         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
133
134         /*
135          * No locking available for sched_info (and too expensive to add one)
136          * Mitigate by taking snapshot of values
137          */
138         t1 = tsk->sched_info.pcnt;
139         t2 = tsk->sched_info.run_delay;
140         t3 = tsk->sched_info.cpu_time;
141
142         d->cpu_count += t1;
143
144         jiffies_to_timespec(t2, &ts);
145         tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
146         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
147
148         tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
149         d->cpu_run_virtual_total =
150                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
151
152         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
153
154         spin_lock(&tsk->delays->lock);
155         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
156         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
157         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
158         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
159         d->blkio_count += tsk->delays->blkio_count;
160         d->swapin_count += tsk->delays->swapin_count;
161         spin_unlock(&tsk->delays->lock);
162
163 done:
164         spin_unlock(&tsk->delays_lock);
165         return 0;
166 }
167
168 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
169 {
170         __u64 ret;
171
172         spin_lock(&tsk->delays->lock);
173         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
174                                 tsk->delays->swapin_delay);
175         spin_unlock(&tsk->delays->lock);
176         return ret;
177 }
178