From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752102Ab3LKB0J (ORCPT ); Tue, 10 Dec 2013 20:26:09 -0500 Received: from mail-pb0-f48.google.com ([209.85.160.48]:55159 "EHLO mail-pb0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750782Ab3LKB0G (ORCPT ); Tue, 10 Dec 2013 20:26:06 -0500 Message-ID: <52A7BF24.1080101@linaro.org> Date: Wed, 11 Dec 2013 09:25:56 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Daniel Lezcano , Mike Galbraith CC: Linux Kernel Mailing List , Ingo Molnar Subject: Re: [question] sched: idle_avg and migration latency References: <52A6FB5C.7010706@linaro.org> <1386688302.6304.30.camel@marge.simpson.net> <52A75DE6.8090901@linaro.org> In-Reply-To: <52A75DE6.8090901@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/11/2013 02:31 AM, Daniel Lezcano wrote: >> >> That has changed a little recently. I originally slammed avg_idle >> itself straight to max to ensure that a bursty load would idle balance, >> and not use stale data. If you start cross core switching at high >> frequency, you'll still shut idle balancing quickly. > > Ok, thanks for the explanation. > > I think I am a bit puzzled with the 'idle_avg' name. I am guessing the > semantic of this variable is "how long this cpu has been idle". > > The idle duration, with the no_hz, could be long, several seconds if the > work queues have been migrated and if the timer affinity is set to > another cpu. So if we fall in this case and there is a burst of activity > + micro-idle and idle_avg is not leverage to max, it will stay high > during an amount of time, thus pulling tasks at each micro idle period, > right ? yes, I think so. -- Thanks Alex