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Commit af6ace76 authored by Dario Faggioli's avatar Dario Faggioli Committed by Ingo Molnar
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sched/deadline: Add latency tracing for SCHED_DEADLINE tasks 



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: default avatarDario Faggioli <raistlin@linux.it>
Signed-off-by: default avatarJuri Lelli <juri.lelli@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1383831828-15501-9-git-send-email-juri.lelli@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 755378a4

kernel/trace/trace_sched_wakeup.c

+60 −4
Original line number Diff line number Diff line
@@ -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);

kernel/trace/trace_selftest.c

+19 −14
Original line number Diff line number Diff line
@@ -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();