Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6.git] / kernel / latencytop.c
1 /*
2  * latencytop.c: Latency display infrastructure
3  *
4  * (C) Copyright 2008 Intel Corporation
5  * Author: Arjan van de Ven <arjan@linux.intel.com>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; version 2
10  * of the License.
11  */
12 #include <linux/latencytop.h>
13 #include <linux/kallsyms.h>
14 #include <linux/seq_file.h>
15 #include <linux/notifier.h>
16 #include <linux/spinlock.h>
17 #include <linux/proc_fs.h>
18 #include <linux/module.h>
19 #include <linux/sched.h>
20 #include <linux/list.h>
21 #include <linux/slab.h>
22 #include <linux/stacktrace.h>
23
24 static DEFINE_SPINLOCK(latency_lock);
25
26 #define MAXLR 128
27 static struct latency_record latency_record[MAXLR];
28
29 int latencytop_enabled;
30
31 void clear_all_latency_tracing(struct task_struct *p)
32 {
33         unsigned long flags;
34
35         if (!latencytop_enabled)
36                 return;
37
38         spin_lock_irqsave(&latency_lock, flags);
39         memset(&p->latency_record, 0, sizeof(p->latency_record));
40         p->latency_record_count = 0;
41         spin_unlock_irqrestore(&latency_lock, flags);
42 }
43
44 static void clear_global_latency_tracing(void)
45 {
46         unsigned long flags;
47
48         spin_lock_irqsave(&latency_lock, flags);
49         memset(&latency_record, 0, sizeof(latency_record));
50         spin_unlock_irqrestore(&latency_lock, flags);
51 }
52
53 static void __sched
54 account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
55 {
56         int firstnonnull = MAXLR + 1;
57         int i;
58
59         if (!latencytop_enabled)
60                 return;
61
62         /* skip kernel threads for now */
63         if (!tsk->mm)
64                 return;
65
66         for (i = 0; i < MAXLR; i++) {
67                 int q, same = 1;
68
69                 /* Nothing stored: */
70                 if (!latency_record[i].backtrace[0]) {
71                         if (firstnonnull > i)
72                                 firstnonnull = i;
73                         continue;
74                 }
75                 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
76                         unsigned long record = lat->backtrace[q];
77
78                         if (latency_record[i].backtrace[q] != record) {
79                                 same = 0;
80                                 break;
81                         }
82
83                         /* 0 and ULONG_MAX entries mean end of backtrace: */
84                         if (record == 0 || record == ULONG_MAX)
85                                 break;
86                 }
87                 if (same) {
88                         latency_record[i].count++;
89                         latency_record[i].time += lat->time;
90                         if (lat->time > latency_record[i].max)
91                                 latency_record[i].max = lat->time;
92                         return;
93                 }
94         }
95
96         i = firstnonnull;
97         if (i >= MAXLR - 1)
98                 return;
99
100         /* Allocted a new one: */
101         memcpy(&latency_record[i], lat, sizeof(struct latency_record));
102 }
103
104 static inline void store_stacktrace(struct task_struct *tsk, struct latency_record *lat)
105 {
106         struct stack_trace trace;
107
108         memset(&trace, 0, sizeof(trace));
109         trace.max_entries = LT_BACKTRACEDEPTH;
110         trace.entries = &lat->backtrace[0];
111         trace.skip = 0;
112         save_stack_trace_tsk(tsk, &trace);
113 }
114
115 void __sched
116 account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
117 {
118         unsigned long flags;
119         int i, q;
120         struct latency_record lat;
121
122         if (!latencytop_enabled)
123                 return;
124
125         /* Long interruptible waits are generally user requested... */
126         if (inter && usecs > 5000)
127                 return;
128
129         memset(&lat, 0, sizeof(lat));
130         lat.count = 1;
131         lat.time = usecs;
132         lat.max = usecs;
133         store_stacktrace(tsk, &lat);
134
135         spin_lock_irqsave(&latency_lock, flags);
136
137         account_global_scheduler_latency(tsk, &lat);
138
139         /*
140          * short term hack; if we're > 32 we stop; future we recycle:
141          */
142         tsk->latency_record_count++;
143         if (tsk->latency_record_count >= LT_SAVECOUNT)
144                 goto out_unlock;
145
146         for (i = 0; i < LT_SAVECOUNT ; i++) {
147                 struct latency_record *mylat;
148                 int same = 1;
149
150                 mylat = &tsk->latency_record[i];
151                 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
152                         unsigned long record = lat.backtrace[q];
153
154                         if (mylat->backtrace[q] != record) {
155                                 same = 0;
156                                 break;
157                         }
158
159                         /* 0 and ULONG_MAX entries mean end of backtrace: */
160                         if (record == 0 || record == ULONG_MAX)
161                                 break;
162                 }
163                 if (same) {
164                         mylat->count++;
165                         mylat->time += lat.time;
166                         if (lat.time > mylat->max)
167                                 mylat->max = lat.time;
168                         goto out_unlock;
169                 }
170         }
171
172         /* Allocated a new one: */
173         i = tsk->latency_record_count;
174         memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
175
176 out_unlock:
177         spin_unlock_irqrestore(&latency_lock, flags);
178 }
179
180 static int lstats_show(struct seq_file *m, void *v)
181 {
182         int i;
183
184         seq_puts(m, "Latency Top version : v0.1\n");
185
186         for (i = 0; i < MAXLR; i++) {
187                 if (latency_record[i].backtrace[0]) {
188                         int q;
189                         seq_printf(m, "%i %li %li ",
190                                 latency_record[i].count,
191                                 latency_record[i].time,
192                                 latency_record[i].max);
193                         for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
194                                 char sym[KSYM_NAME_LEN];
195                                 char *c;
196                                 if (!latency_record[i].backtrace[q])
197                                         break;
198                                 if (latency_record[i].backtrace[q] == ULONG_MAX)
199                                         break;
200                                 sprint_symbol(sym, latency_record[i].backtrace[q]);
201                                 c = strchr(sym, '+');
202                                 if (c)
203                                         *c = 0;
204                                 seq_printf(m, "%s ", sym);
205                         }
206                         seq_printf(m, "\n");
207                 }
208         }
209         return 0;
210 }
211
212 static ssize_t
213 lstats_write(struct file *file, const char __user *buf, size_t count,
214              loff_t *offs)
215 {
216         clear_global_latency_tracing();
217
218         return count;
219 }
220
221 static int lstats_open(struct inode *inode, struct file *filp)
222 {
223         return single_open(filp, lstats_show, NULL);
224 }
225
226 static struct file_operations lstats_fops = {
227         .open           = lstats_open,
228         .read           = seq_read,
229         .write          = lstats_write,
230         .llseek         = seq_lseek,
231         .release        = single_release,
232 };
233
234 static int __init init_lstats_procfs(void)
235 {
236         proc_create("latency_stats", 0644, NULL, &lstats_fops);
237         return 0;
238 }
239 __initcall(init_lstats_procfs);