linux-kernel - Re: [PATCH] sched,trace: Allow tracing the preemption decision on wakeup

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Message-ID: <CAPM31RK-fSJj9o2PhgJ05wHBSStbf6hx4F8Nv=inB90x4Sx=VQ@mail.gmail.com>
Date:	Thu, 14 Mar 2013 08:42:43 -0700
From:	Paul Turner <pjt@...gle.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, tglx <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched,trace: Allow tracing the preemption decision on wakeup

Yeah -- this one is a real no brainer to move; looks good :)

On Thu, Mar 14, 2013 at 5:00 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 2013-03-14 at 10:48 +0100, Peter Zijlstra wrote:
>> Thomas noted that we do the wakeup preemption check after the wakeup
>> trace point, this means the tracepoint cannot test/report this decision;
>> which is rather important for latency sensitive workloads. Therefore
>> move the tracepoint after doing the preemption check.
>>
>> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
>> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>
> Acked-by: Steven Rostedt <rostedt@...dmis.org>
>
>> ---
>>  kernel/sched/core.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index b36635e..849deb9 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
>>  static void
>>  ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
>>  {
>> -     trace_sched_wakeup(p, true);
>>       check_preempt_curr(rq, p, wake_flags);
>> +     trace_sched_wakeup(p, true);
>>
>>       p->state = TASK_RUNNING;
>>  #ifdef CONFIG_SMP
>>
>
>
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