linux-kernel - Re: [PATCH RFC/TEST] sched: make sync affine wakeups work

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Date:	Fri, 02 May 2014 09:37:53 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-kernel@...r.kernel.org, morten.rasmussen@....com,
	mingo@...nel.org, peterz@...radead.org,
	george.mccollister@...il.com, ktkhai@...allels.com
Subject: Re: [PATCH RFC/TEST] sched: make sync affine wakeups work

On Fri, 2014-05-02 at 02:30 -0400, Rik van Riel wrote: 
> On 05/02/2014 02:13 AM, Mike Galbraith wrote:
> > On Fri, 2014-05-02 at 00:42 -0400, Rik van Riel wrote:
> > 
> >> Whether or not this is the right thing to do remains to be seen,
> >> but it does allow us to verify whether or not the wake_affine
> >> strategy of always doing affine wakeups and only disabling them
> >> in a specific circumstance is sound, or needs rethinking...
> > 
> > Yes, it needs rethinking.
> > 
> > I know why you want to try this, yes, select_idle_sibling() is very much
> > a two faced little bitch.
> 
> My biggest problem with select_idle_sibling and wake_affine in
> general is that it will override NUMA placement, even when
> processes only wake each other up infrequently...

Hm, seems the thing to do would be to tell select_task_rq_fair() to keep
it's mitts off of tasks that the numasched stuff has placed rather than
decapitating select_idle_sibling() or some other drastic measure.

-Mike

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