From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151AbcEWNAu (ORCPT ); Mon, 23 May 2016 09:00:50 -0400 Received: from mx2.suse.de ([195.135.220.15]:40594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753899AbcEWNAt (ORCPT ); Mon, 23 May 2016 09:00:49 -0400 Message-ID: <1464008446.4537.130.camel@suse.de> Subject: Re: [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in wake_wide From: Mike Galbraith To: Morten Rasmussen Cc: peterz@infradead.org, mingo@redhat.com, dietmar.eggemann@arm.com, yuyang.du@intel.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org Date: Mon, 23 May 2016 15:00:46 +0200 In-Reply-To: <20160523120010.GB27946@e105550-lin.cambridge.arm.com> References: <1464001138-25063-1-git-send-email-morten.rasmussen@arm.com> <1464001138-25063-4-git-send-email-morten.rasmussen@arm.com> <1464001927.4537.118.camel@suse.de> <20160523120010.GB27946@e105550-lin.cambridge.arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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