From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753126Ab2H2Ujh (ORCPT ); Wed, 29 Aug 2012 16:39:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10790 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000Ab2H2Ujg (ORCPT ); Wed, 29 Aug 2012 16:39:36 -0400 Message-ID: <503E7E6D.8030302@redhat.com> Date: Wed, 29 Aug 2012 16:41:17 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Linux kernel Mailing List CC: Matthew Garrett , Arjan van de Ven , Boris Ostrovsky , Len Brown , Deepthi Dharwar , ShuoX Liu Subject: Re: KS/Plumbers: c-state governor BOF References: <5037B36A.8000209@redhat.com> In-Reply-To: <5037B36A.8000209@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/24/2012 01:01 PM, Rik van Riel wrote: > Since a good number of us will be in San Diego next week, at > Kernel Summit / Plumbers / etc, I will organize a c-state > governor BOF for those who are interested. Here are the note from today's c-state governor BOF session: - idle time estimator can be improved to return more conservative values - have a trace point to verify how well idle time estimation works, returning expected idle time for the current algorithm, expected idle time for a test algorithm, and actually measured idle time - we can objectively measure whether one idle time estimation algorithm is better than another - example: last 8 idle times are 180 200 30 210 1000 150 10000 190 - average idle time around 1500, but not typical - typical idle time just under 200 - almost all idle time spent in one interval - scheduler and cpufreq people also want idle time statistics, idea is to move the idle time statistics to the scheduler - having idle time statistics in the scheduler allows the stats to be migrated when the scheduler migrates a task - interface: expected idle time, demotion time - if we sleep much more than the expected idle time, put CPU into a deeper c-state - on x86 timed mwait could be used - generic timer code would be usable too - take into account both the idle statistics and power break-even