linux-kernel - Re: [PATCH RFC] sched,idle: teach select_idle

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Date:	Fri, 03 Oct 2014 08:23:04 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH RFC] sched,idle: teach select_idle_sibling about idle
 states

On Thu, 2014-10-02 at 13:15 -0400, Rik van Riel wrote:

> Subject: sched,idle: teach select_idle_sibling about idle states
> 
> Change select_idle_sibling to take cpu idle exit latency into
> account.  First preference is to select the cpu with the lowest
> exit latency from a completely idle sched_group inside the CPU;
> if that is not available, we pick the CPU with the lowest exit
> latency in any sched_group.
> 
> This increases the total search time of select_idle_sibling,
> we may want to look into propagating load info up the sched_group
> tree in some way. That information would also be useful to prevent
> the wake_affine logic from causing a load imbalance between
> sched_groups.

A generic boo hiss aimed in the general direction of all of this let's
go look at every possibility on every wakeup stuff.  Less is more.

-Mike

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