linux-kernel - Re: [PATCH] sched: Move the wakeup tracepoint from ttwu_do_wakeup() to ttwu

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Date:	Tue, 6 May 2014 10:29:56 +0900
From:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	<peterz@...radead.org>, <bsegall@...gle.com>, <mingo@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: Move the wakeup tracepoint from ttwu_do_wakeup()
 to ttwu_activate().

On 05/06/2014 11:06 AM, Steven Rostedt wrote:
> On Tue, 6 May 2014 09:19:51 +0900
> Dongsheng Yang <yangds.fnst@...fujitsu.com> wrote:
>
> I wonder if we should have the event, or way to distinguish the
> difference. Hmm, there's that "success" parameter in the tracepoint.
> Could we possible be able to trace events where the success is true
> only if it was actually waking the event, and false otherwise?
>
> Having the sched_wakeup trace event show you when something woke the
> task up may still be useful information. For example, you add yourself
> to a wait queue and want to see the "wakeup". If we only show it for
> tasks that really woke up then we wont see it for those that added
> itself to a waitqueue but was "woken" before it could schedule out.
>
> The original sched_wakeup did this, but with the ttwu rewrite, it was
> lost.

Ha, got what you mean. Yes, we can take the use of success in sched_wakeup
event.
>
> Something like below?
>
> -- Steve
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 268a45e..e583989 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1404,6 +1404,7 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
>   {
>   	activate_task(rq, p, en_flags);
>   	p->on_rq = 1;
> +	trace_sched_wakeup(p, true);
>   
>   	/* if a worker is waking up, notify workqueue */
>   	if (p->flags & PF_WQ_WORKER)
> @@ -1417,7 +1418,6 @@ 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;
>   #ifdef CONFIG_SMP
> @@ -1662,6 +1662,8 @@ static void try_to_wake_up_local(struct task_struct *p)
>   
>   	if (!p->on_rq)
>   		ttwu_activate(rq, p, ENQUEUE_WAKEUP);
> +	else
> +		trace_sched_wakeup(p, false);

Also we should add a false trace point in ttwu_remote().
>   
>   	ttwu_do_wakeup(rq, p, 0);
>   	ttwu_stat(p, smp_processor_id(), 0);

Thanx steven, I will send a new patch as you suggested here.
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