aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/trace/trace_sched_wakeup.c
diff options
context:
space:
mode:
authorSteven Rostedt <srostedt@redhat.com>2008-05-12 15:20:42 -0400
committerThomas Gleixner <tglx@linutronix.de>2008-05-23 14:32:36 -0400
commit352ad25aa4a189c667cb2af333948d34692a2d27 (patch)
tree83a11c626b3818711d3b88061964c9ea603f7b68 /kernel/trace/trace_sched_wakeup.c
parent35e8e302e5d6e32675df2fc1dd3a53dfa6630dc1 (diff)
ftrace: tracer for scheduler wakeup latency
This patch adds the tracer that tracks the wakeup latency of the highest priority waking task. "wakeup" is added to /debugfs/tracing/available_tracers Also added to /debugfs/tracing tracing_max_latency holds the current max latency for the wakeup wakeup_thresh if set to other than zero, a log will be recorded for every wakeup that takes longer than the number entered in here (usecs for all counters) (deletes previous trace) Examples: (with ftrace_enabled = 0) ============ preemption latency trace v1.1.5 on 2.6.24-rc8 Signed-off-by: Ingo Molnar <mingo@elte.hu> -------------------------------------------------------------------- latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2) ----------------- | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99) ----------------- _------=> CPU# / _-----=> irqs-off | / _----=> need-resched || / _---=> hardirq/softirq ||| / _--=> preempt-depth |||| / ||||| delay cmd pid ||||| time | caller \ / ||||| \ | / quilt-8551 0d..3 0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>) quilt-8551 0d..4 26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>) vim:ft=help ============ (with ftrace_enabled = 1) ============ preemption latency trace v1.1.5 on 2.6.24-rc8 -------------------------------------------------------------------- latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2) ----------------- | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99) ----------------- _------=> CPU# / _-----=> irqs-off | / _----=> need-resched || / _---=> hardirq/softirq ||| / _--=> preempt-depth |||| / ||||| delay cmd pid ||||| time | caller \ / ||||| \ | / bash-10653 1d..3 0us : wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>) bash-10653 1d..3 1us : try_to_wake_up+0x271/0x2e7 <ffffffff80233dcf> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>) bash-10653 1d..2 2us : try_to_wake_up+0x296/0x2e7 <ffffffff80233df4> (update_rq_clock+0x9/0x20 <ffffffff802303f3>) bash-10653 1d..2 2us : update_rq_clock+0x1e/0x20 <ffffffff80230408> (__update_rq_clock+0xc/0x90 <ffffffff80230366>) bash-10653 1d..2 3us : __update_rq_clock+0x1b/0x90 <ffffffff80230375> (sched_clock+0x9/0x29 <ffffffff80214529>) bash-10653 1d..2 4us : try_to_wake_up+0x2a6/0x2e7 <ffffffff80233e04> (activate_task+0xc/0x3f <ffffffff8022ffca>) bash-10653 1d..2 4us : activate_task+0x2d/0x3f <ffffffff8022ffeb> (enqueue_task+0xe/0x66 <ffffffff8022ff66>) bash-10653 1d..2 5us : enqueue_task+0x5b/0x66 <ffffffff8022ffb3> (enqueue_task_rt+0x9/0x3c <ffffffff80233351>) bash-10653 1d..2 6us : try_to_wake_up+0x2ba/0x2e7 <ffffffff80233e18> (check_preempt_wakeup+0x12/0x99 <ffffffff80234f84>) [...] bash-10653 1d..5 33us : tracing_record_cmdline+0xcf/0xd4 <ffffffff80338aad> (_spin_unlock+0x9/0x33 <ffffffff8048d3ec>) bash-10653 1d..5 34us : _spin_unlock+0x19/0x33 <ffffffff8048d3fc> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>) bash-10653 1d..4 35us : wakeup_sched_switch+0x65/0x2ff <ffffffff80339f66> (_spin_lock_irqsave+0xc/0xa9 <ffffffff8048d08b>) bash-10653 1d..4 35us : _spin_lock_irqsave+0x19/0xa9 <ffffffff8048d098> (add_preempt_count+0xe/0x77 <ffffffff8023311a>) bash-10653 1d..4 36us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>) vim:ft=help ============ The [...] was added here to not waste your email box space. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/trace/trace_sched_wakeup.c')
-rw-r--r--kernel/trace/trace_sched_wakeup.c310
1 files changed, 310 insertions, 0 deletions
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
new file mode 100644
index 000000000000..7c3ccefcf4c3
--- /dev/null
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -0,0 +1,310 @@
1/*
2 * trace task wakeup timings
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6 *
7 * Based on code from the latency_tracer, that is:
8 *
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 William Lee Irwin III
11 */
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/debugfs.h>
15#include <linux/kallsyms.h>
16#include <linux/uaccess.h>
17#include <linux/ftrace.h>
18
19#include "trace.h"
20
21static struct trace_array *wakeup_trace;
22static int __read_mostly tracer_enabled;
23
24static struct task_struct *wakeup_task;
25static int wakeup_cpu;
26static unsigned wakeup_prio = -1;
27
28static DEFINE_SPINLOCK(wakeup_lock);
29
30static void notrace __wakeup_reset(struct trace_array *tr);
31
32/*
33 * Should this new latency be reported/recorded?
34 */
35static int notrace report_latency(cycle_t delta)
36{
37 if (tracing_thresh) {
38 if (delta < tracing_thresh)
39 return 0;
40 } else {
41 if (delta <= tracing_max_latency)
42 return 0;
43 }
44 return 1;
45}
46
47void notrace
48wakeup_sched_switch(struct task_struct *prev, struct task_struct *next)
49{
50 unsigned long latency = 0, t0 = 0, t1 = 0;
51 struct trace_array *tr = wakeup_trace;
52 struct trace_array_cpu *data;
53 cycle_t T0, T1, delta;
54 unsigned long flags;
55 long disabled;
56 int cpu;
57
58 if (unlikely(!tracer_enabled))
59 return;
60
61 /*
62 * When we start a new trace, we set wakeup_task to NULL
63 * and then set tracer_enabled = 1. We want to make sure
64 * that another CPU does not see the tracer_enabled = 1
65 * and the wakeup_task with an older task, that might
66 * actually be the same as next.
67 */
68 smp_rmb();
69
70 if (next != wakeup_task)
71 return;
72
73 /* The task we are waitng for is waking up */
74 data = tr->data[wakeup_cpu];
75
76 /* disable local data, not wakeup_cpu data */
77 cpu = raw_smp_processor_id();
78 disabled = atomic_inc_return(&tr->data[cpu]->disabled);
79 if (likely(disabled != 1))
80 goto out;
81
82 spin_lock_irqsave(&wakeup_lock, flags);
83
84 /* We could race with grabbing wakeup_lock */
85 if (unlikely(!tracer_enabled || next != wakeup_task))
86 goto out_unlock;
87
88 ftrace(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
89
90 /*
91 * usecs conversion is slow so we try to delay the conversion
92 * as long as possible:
93 */
94 T0 = data->preempt_timestamp;
95 T1 = now(cpu);
96 delta = T1-T0;
97
98 if (!report_latency(delta))
99 goto out_unlock;
100
101 latency = nsecs_to_usecs(delta);
102
103 tracing_max_latency = delta;
104 t0 = nsecs_to_usecs(T0);
105 t1 = nsecs_to_usecs(T1);
106
107 update_max_tr(tr, wakeup_task, wakeup_cpu);
108
109 if (tracing_thresh) {
110 printk(KERN_INFO "(%16s-%-5d|#%d): %lu us wakeup latency "
111 "violates %lu us threshold.\n"
112 " => started at timestamp %lu: ",
113 wakeup_task->comm, wakeup_task->pid,
114 raw_smp_processor_id(),
115 latency, nsecs_to_usecs(tracing_thresh), t0);
116 } else {
117 printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us maximum "
118 "wakeup latency.\n => started at timestamp %lu: ",
119 wakeup_task->comm, wakeup_task->pid,
120 cpu, latency, t0);
121 }
122
123 printk(KERN_CONT " ended at timestamp %lu: ", t1);
124 dump_stack();
125 t1 = nsecs_to_usecs(now(cpu));
126 printk(KERN_CONT " dump-end timestamp %lu\n\n", t1);
127
128out_unlock:
129 __wakeup_reset(tr);
130 spin_unlock_irqrestore(&wakeup_lock, flags);
131out:
132 atomic_dec(&tr->data[cpu]->disabled);
133}
134
135static void notrace __wakeup_reset(struct trace_array *tr)
136{
137 struct trace_array_cpu *data;
138 int cpu;
139
140 assert_spin_locked(&wakeup_lock);
141
142 for_each_possible_cpu(cpu) {
143 data = tr->data[cpu];
144 tracing_reset(data);
145 }
146
147 wakeup_cpu = -1;
148 wakeup_prio = -1;
149
150 if (wakeup_task)
151 put_task_struct(wakeup_task);
152
153 wakeup_task = NULL;
154}
155
156static void notrace wakeup_reset(struct trace_array *tr)
157{
158 unsigned long flags;
159
160 spin_lock_irqsave(&wakeup_lock, flags);
161 __wakeup_reset(tr);
162 spin_unlock_irqrestore(&wakeup_lock, flags);
163}
164
165static notrace void
166wakeup_check_start(struct trace_array *tr, struct task_struct *p,
167 struct task_struct *curr)
168{
169 int cpu = smp_processor_id();
170 unsigned long flags;
171 long disabled;
172
173 if (likely(!rt_task(p)) ||
174 p->prio >= wakeup_prio ||
175 p->prio >= curr->prio)
176 return;
177
178 disabled = atomic_inc_return(&tr->data[cpu]->disabled);
179 if (unlikely(disabled != 1))
180 goto out;
181
182 /* interrupts should be off from try_to_wake_up */
183 spin_lock(&wakeup_lock);
184
185 /* check for races. */
186 if (!tracer_enabled || p->prio >= wakeup_prio)
187 goto out_locked;
188
189 /* reset the trace */
190 __wakeup_reset(tr);
191
192 wakeup_cpu = task_cpu(p);
193 wakeup_prio = p->prio;
194
195 wakeup_task = p;
196 get_task_struct(wakeup_task);
197
198 local_save_flags(flags);
199
200 tr->data[wakeup_cpu]->preempt_timestamp = now(cpu);
201 ftrace(tr, tr->data[wakeup_cpu], CALLER_ADDR1, CALLER_ADDR2, flags);
202
203out_locked:
204 spin_unlock(&wakeup_lock);
205out:
206 atomic_dec(&tr->data[cpu]->disabled);
207}
208
209notrace void
210ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
211{
212 if (likely(!tracer_enabled))
213 return;
214
215 wakeup_check_start(wakeup_trace, wakee, curr);
216}
217
218notrace void
219ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr)
220{
221 if (likely(!tracer_enabled))
222 return;
223
224 wakeup_check_start(wakeup_trace, wakee, curr);
225}
226
227static notrace void start_wakeup_tracer(struct trace_array *tr)
228{
229 wakeup_reset(tr);
230
231 /*
232 * Don't let the tracer_enabled = 1 show up before
233 * the wakeup_task is reset. This may be overkill since
234 * wakeup_reset does a spin_unlock after setting the
235 * wakeup_task to NULL, but I want to be safe.
236 * This is a slow path anyway.
237 */
238 smp_wmb();
239
240 tracer_enabled = 1;
241
242 return;
243}
244
245static notrace void stop_wakeup_tracer(struct trace_array *tr)
246{
247 tracer_enabled = 0;
248}
249
250static notrace void wakeup_tracer_init(struct trace_array *tr)
251{
252 wakeup_trace = tr;
253
254 if (tr->ctrl)
255 start_wakeup_tracer(tr);
256}
257
258static notrace void wakeup_tracer_reset(struct trace_array *tr)
259{
260 if (tr->ctrl) {
261 stop_wakeup_tracer(tr);
262 /* make sure we put back any tasks we are tracing */
263 wakeup_reset(tr);
264 }
265}
266
267static void wakeup_tracer_ctrl_update(struct trace_array *tr)
268{
269 if (tr->ctrl)
270 start_wakeup_tracer(tr);
271 else
272 stop_wakeup_tracer(tr);
273}
274
275static void notrace wakeup_tracer_open(struct trace_iterator *iter)
276{
277 /* stop the trace while dumping */
278 if (iter->tr->ctrl)
279 stop_wakeup_tracer(iter->tr);
280}
281
282static void notrace wakeup_tracer_close(struct trace_iterator *iter)
283{
284 /* forget about any processes we were recording */
285 if (iter->tr->ctrl)
286 start_wakeup_tracer(iter->tr);
287}
288
289static struct tracer wakeup_tracer __read_mostly =
290{
291 .name = "wakeup",
292 .init = wakeup_tracer_init,
293 .reset = wakeup_tracer_reset,
294 .open = wakeup_tracer_open,
295 .close = wakeup_tracer_close,
296 .ctrl_update = wakeup_tracer_ctrl_update,
297 .print_max = 1,
298};
299
300__init static int init_wakeup_tracer(void)
301{
302 int ret;
303
304 ret = register_tracer(&wakeup_tracer);
305 if (ret)
306 return ret;
307
308 return 0;
309}
310device_initcall(init_wakeup_tracer);