linux-kernel - Re: [v2 patch v3.18+ regression fix] sched: Further improve spurious CPU

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Message-ID: <1473167264.32128.5.camel@gmail.com>
Date:   Tue, 06 Sep 2016 15:07:44 +0200
From:   Mike Galbraith <umgwanakikbuti@...il.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [v2 patch v3.18+ regression fix] sched: Further improve
 spurious CPU_IDLE active migrations

On Tue, 2016-09-06 at 15:01 +0200, Vincent Guittot wrote:
> Le Monday 05 Sep 2016 à 18:26:53 (+0200), Mike Galbraith a écrit :
> > Coming back to this, how about this instead, only increase the group
> > imbalance threshold when sd_llc_size == 2.  Newer L3 equipped
> > processors then aren't affected.
> > 
> 
> Not sure that all systems with sd_llc_size == 2 wants this behavior.
> 
> Why not adding a sched_feature for changing the 2nd half of the test
> for some systems ?

Because users won't know, and shouldn't need to know that they need to
flip that switch.

	-Mike