Commit fbd705a0 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Introduce the 'trace_sched_waking' tracepoint 



Mathieu reported that since 317f3941 ("sched: Move the second half
of ttwu() to the remote cpu") trace_sched_wakeup() can happen out of
context of the waker.

This is a problem when you want to analyse wakeup paths because it is
now very hard to correlate the wakeup event to whoever issued the
wakeup.

OTOH trace_sched_wakeup() is issued at the point where we set
p->state = TASK_RUNNING, which is right were we hand the task off to
the scheduler, so this is an important point when looking at
scheduling behaviour, up to here its been the wakeup path everything
hereafter is due to scheduler policy.

To bridge this gap, introduce a second tracepoint: trace_sched_waking.
It is guaranteed to be called in the waker context.

Reported-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Francis Giraldeau <francis.giraldeau@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150609091336.GQ3644@twins.programming.kicks-ass.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9d7fb042

include/trace/events/sched.h

+21 −9
Original line number Diff line number Diff line
@@ -55,9 +55,9 @@ TRACE_EVENT(sched_kthread_stop_ret, 
 */

DECLARE_EVENT_CLASS(sched_wakeup_template,



	TP_PROTO(struct task_struct *p, int success),

	TP_PROTO(struct task_struct *p),



	TP_ARGS(__perf_task(p), success),

	TP_ARGS(__perf_task(p)),



	TP_STRUCT__entry(

		__array(	char,	comm,	TASK_COMM_LEN	)
@@ -71,25 +71,37 @@ DECLARE_EVENT_CLASS(sched_wakeup_template, 
		memcpy(__entry->comm, p->comm, TASK_COMM_LEN);

		__entry->pid		= p->pid;

		__entry->prio		= p->prio;

		__entry->success	= success;

		__entry->success	= 1; /* rudiment, kill when possible */

		__entry->target_cpu	= task_cpu(p);

	),



	TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d",

	TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d",

		  __entry->comm, __entry->pid, __entry->prio,

		  __entry->success, __entry->target_cpu)

		  __entry->target_cpu)

);



/*

 * Tracepoint called when waking a task; this tracepoint is guaranteed to be

 * called from the waking context.

 */

DEFINE_EVENT(sched_wakeup_template, sched_waking,

	     TP_PROTO(struct task_struct *p),

	     TP_ARGS(p));



/*

 * Tracepoint called when the task is actually woken; p->state == TASK_RUNNNG.

 * It it not always called from the waking context.

 */

DEFINE_EVENT(sched_wakeup_template, sched_wakeup,

	     TP_PROTO(struct task_struct *p, int success),

	     TP_ARGS(p, success));

	     TP_PROTO(struct task_struct *p),

	     TP_ARGS(p));



/*

 * Tracepoint for waking up a new task:

 */

DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,

	     TP_PROTO(struct task_struct *p, int success),

	     TP_ARGS(p, success));

	     TP_PROTO(struct task_struct *p),

	     TP_ARGS(p));



#ifdef CREATE_TRACE_POINTS

static inline long __trace_sched_switch_state(struct task_struct *p)

kernel/sched/core.c

+7 −3
Original line number Diff line number Diff line
@@ -1654,9 +1654,9 @@ static void 
ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)

{

	check_preempt_curr(rq, p, wake_flags);

	trace_sched_wakeup(p, true);



	p->state = TASK_RUNNING;

	trace_sched_wakeup(p);



#ifdef CONFIG_SMP

	if (p->sched_class->task_woken) {

		/*
@@ -1874,6 +1874,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
	if (!(p->state & state))

		goto out;



	trace_sched_waking(p);



	success = 1; /* we're going to change ->state */

	cpu = task_cpu(p);
@@ -1949,6 +1951,8 @@ static void try_to_wake_up_local(struct task_struct *p) 
	if (!(p->state & TASK_NORMAL))

		goto out;



	trace_sched_waking(p);



	if (!task_on_rq_queued(p))

		ttwu_activate(rq, p, ENQUEUE_WAKEUP);
@@ -2307,7 +2311,7 @@ void wake_up_new_task(struct task_struct *p) 
	rq = __task_rq_lock(p);

	activate_task(rq, p, 0);

	p->on_rq = TASK_ON_RQ_QUEUED;

	trace_sched_wakeup_new(p, true);

	trace_sched_wakeup_new(p);

	check_preempt_curr(rq, p, WF_FORK);

#ifdef CONFIG_SMP

	if (p->sched_class->task_woken)

kernel/trace/trace_sched_switch.c

+1 −1
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ probe_sched_switch(void *ignore, struct task_struct *prev, struct task_struct *n 
}



static void

probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success)

probe_sched_wakeup(void *ignore, struct task_struct *wakee)

{

	if (unlikely(!sched_ref))

		return;

kernel/trace/trace_sched_wakeup.c

+1 −1
Original line number Diff line number Diff line
@@ -514,7 +514,7 @@ static void wakeup_reset(struct trace_array *tr) 
}



static void

probe_wakeup(void *ignore, struct task_struct *p, int success)

probe_wakeup(void *ignore, struct task_struct *p)

{

	struct trace_array_cpu *data;

	int cpu = smp_processor_id();

CRA Git | Maintained and supported by SUSTech CRA and CCSE