linux-kernel - Re: [PATCH] sched/fair: change where we report sched stats

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Message-ID: <5488BFC5.3080001@fb.com>
Date:	Wed, 10 Dec 2014 16:48:53 -0500
From:	Josef Bacik <jbacik@...com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
CC:	<bmaurer@...com>, <rkroll@...com>, <kernel-team@...com>,
	<mingo@...hat.com>, <peterz@...radead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: change where we report sched stats

On 12/10/2014 01:23 AM, Mike Galbraith wrote:
> On Tue, 2014-12-09 at 13:21 -0500, Josef Bacik wrote:
>
>> This patch moves stat stuff to after the schedule, right as we are waking up,
>
> But sleep/block ends when the task is awakened/enqueued, not when it
> gets the CPU.  You're adding scheduling latency, breaking accounting.
>

Yes I'm aware of that.  I don't care if the delay time is slightly 
higher than normal, I care about knowing exactly why we were sleeping to 
begin with.  I suppose I could leave the accounting part where it is and 
then just fire the tracepoint when it's put on the CPU so we get the 
best of both worlds, but honestly I don't feel like adding the extra 
scheduling latency into the accounting is that big of a deal.  Thanks,

Josef

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