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sched/deadline: Add latency tracing for SCHED_DEADLINE tasks

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It is very likely that systems that wants/needs to use the new
SCHED_DEADLINE policy also want to have the scheduling latency of
the -deadline tasks under control.

For this reason a new version of the scheduling wakeup latency,
called "wakeup_dl", is introduced.

As a consequence of applying this patch there will be three wakeup
latency tracer:

 * "wakeup", that deals with all tasks in the system;
 * "wakeup_rt", that deals with -rt and -deadline tasks only;
 * "wakeup_dl", that deals with -deadline tasks only.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1383831828-15501-9-git-send-email-juri.lelli@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dario Faggioli 2013-11-07 14:43:42 +01:00 committed by Ingo Molnar
parent 755378a471
commit af6ace764d
2 changed files with 79 additions and 18 deletions
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64
kernel/trace/trace_sched_wakeup.c
View file

@ -27,6 +27,8 @@ static int wakeup_cpu;
static int wakeup_current_cpu;
static unsigned wakeup_prio = -1;
static int wakeup_rt;
static int wakeup_dl;
static int tracing_dl = 0;
static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
@ -437,6 +439,7 @@ static void __wakeup_reset(struct trace_array *tr)
{
wakeup_cpu = -1;
wakeup_prio = -1;
tracing_dl = 0;
if (wakeup_task)
put_task_struct(wakeup_task);
@ -472,9 +475,17 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
tracing_record_cmdline(p);
tracing_record_cmdline(current);
if ((wakeup_rt && !rt_task(p)) ||
p->prio >= wakeup_prio ||
p->prio >= current->prio)
/*
* Semantic is like this:
* - wakeup tracer handles all tasks in the system, independently
* from their scheduling class;
* - wakeup_rt tracer handles tasks belonging to sched_dl and
* sched_rt class;
* - wakeup_dl handles tasks belonging to sched_dl class only.
*/
if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
(wakeup_rt && !dl_task(p) && !rt_task(p)) ||
(!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
return;
pc = preempt_count();
@ -486,7 +497,8 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
arch_spin_lock(&wakeup_lock);
/* check for races. */
if (!tracer_enabled || p->prio >= wakeup_prio)
if (!tracer_enabled || tracing_dl ||
(!dl_task(p) && p->prio >= wakeup_prio))
goto out_locked;
/* reset the trace */
@ -496,6 +508,15 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
wakeup_current_cpu = wakeup_cpu;
wakeup_prio = p->prio;
/*
* Once you start tracing a -deadline task, don't bother tracing
* another task until the first one wakes up.
*/
if (dl_task(p))
tracing_dl = 1;
else
tracing_dl = 0;
wakeup_task = p;
get_task_struct(wakeup_task);
@ -597,16 +618,25 @@ static int __wakeup_tracer_init(struct trace_array *tr)
static int wakeup_tracer_init(struct trace_array *tr)
{
wakeup_dl = 0;
wakeup_rt = 0;
return __wakeup_tracer_init(tr);
}
static int wakeup_rt_tracer_init(struct trace_array *tr)
{
wakeup_dl = 0;
wakeup_rt = 1;
return __wakeup_tracer_init(tr);
}
static int wakeup_dl_tracer_init(struct trace_array *tr)
{
wakeup_dl = 1;
wakeup_rt = 0;
return __wakeup_tracer_init(tr);
}
static void wakeup_tracer_reset(struct trace_array *tr)
{
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
@ -674,6 +704,28 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.use_max_tr = true,
};
static struct tracer wakeup_dl_tracer __read_mostly =
{
.name = "wakeup_dl",
.init = wakeup_dl_tracer_init,
.reset = wakeup_tracer_reset,
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.wait_pipe = poll_wait_pipe,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.open = wakeup_trace_open,
.close = wakeup_trace_close,
.use_max_tr = true,
};
__init static int init_wakeup_tracer(void)
{
int ret;
@ -686,6 +738,10 @@ __init static int init_wakeup_tracer(void)
if (ret)
return ret;
ret = register_tracer(&wakeup_dl_tracer);
if (ret)
return ret;
return 0;
}
core_initcall(init_wakeup_tracer);

33
kernel/trace/trace_selftest.c
View file

@ -1022,11 +1022,16 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
#ifdef CONFIG_SCHED_TRACER
static int trace_wakeup_test_thread(void *data)
{
/* Make this a RT thread, doesn't need to be too high */
static const struct sched_param param = { .sched_priority = 5 };
/* Make this a -deadline thread */
static const struct sched_attr attr = {
.sched_policy = SCHED_DEADLINE,
.sched_runtime = 100000ULL,
.sched_deadline = 10000000ULL,
.sched_period = 10000000ULL
};
struct completion *x = data;
sched_setscheduler(current, SCHED_FIFO, &param);
sched_setattr(current, &attr);
/* Make it know we have a new prio */
complete(x);
@ -1040,8 +1045,8 @@ static int trace_wakeup_test_thread(void *data)
/* we are awake, now wait to disappear */
while (!kthread_should_stop()) {
/*
* This is an RT task, do short sleeps to let
* others run.
* This will likely be the system top priority
* task, do short sleeps to let others run.
*/
msleep(100);
}
@ -1054,21 +1059,21 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
{
unsigned long save_max = tracing_max_latency;
struct task_struct *p;
struct completion isrt;
struct completion is_ready;
unsigned long count;
int ret;
init_completion(&isrt);
init_completion(&is_ready);
/* create a high prio thread */
p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
/* create a -deadline thread */
p = kthread_run(trace_wakeup_test_thread, &is_ready, "ftrace-test");
if (IS_ERR(p)) {
printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
return -1;
}
/* make sure the thread is running at an RT prio */
wait_for_completion(&isrt);
/* make sure the thread is running at -deadline policy */
wait_for_completion(&is_ready);
/* start the tracing */
ret = tracer_init(trace, tr);
@ -1082,19 +1087,19 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
while (p->on_rq) {
/*
* Sleep to make sure the RT thread is asleep too.
* Sleep to make sure the -deadline thread is asleep too.
* On virtual machines we can't rely on timings,
* but we want to make sure this test still works.
*/
msleep(100);
}
init_completion(&isrt);
init_completion(&is_ready);
wake_up_process(p);
/* Wait for the task to wake up */
wait_for_completion(&isrt);
wait_for_completion(&is_ready);
/* stop the tracing. */
tracing_stop();