linux-kernel - Re: [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in wake

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Date:	Mon, 23 May 2016 15:00:46 +0200
From:	Mike Galbraith <mgalbraith@...e.de>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	peterz@...radead.org, mingo@...hat.com, dietmar.eggemann@....com,
	yuyang.du@...el.com, vincent.guittot@...aro.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in
 wake_wide

On Mon, 2016-05-23 at 13:00 +0100, Morten Rasmussen wrote:

> The problem then seems to be distinguishing truly idle and busy doing
> interrupts. The issue that I observe is that wake_wide() likes pushing
> tasks around in lightly scenarios which isn't desirable for power
> management. Selecting the same cpu again may potentially let others
> reach deeper C-state.
> 
> With that in mind I will if I can do better. Suggestions are welcome :-)

None here.  For big boxen that are highly idle, you'd likely want to
shut down nodes and consolidate load, but otoh, all that slows response
to burst, which I hate.  I prefer race to idle, let power gating do its
job.  If I had a server farm with enough capacity vs load variability
to worry about, I suspect I'd become highly interested in routing.

	-Mike