Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755160AbcDATty (ORCPT ); Fri, 1 Apr 2016 15:49:54 -0400 Received: from casper.infradead.org ([85.118.1.10]:55855 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755074AbcDATtw (ORCPT ); Fri, 1 Apr 2016 15:49:52 -0400 Date: Fri, 1 Apr 2016 21:49:48 +0200 From: Peter Zijlstra To: Leo Yan Cc: Ingo Molnar , Morten Rasmussen , Dietmar Eggemann , Vincent Guittot , Steve Muckle , linux-kernel@vger.kernel.org, eas-dev@lists.linaro.org Subject: Re: [PATCH RFC] sched/fair: let cpu's cfs_rq to reflect task migration Message-ID: <20160401194948.GN3448@twins.programming.kicks-ass.net> References: <1459528717-17339-1-git-send-email-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1459528717-17339-1-git-send-email-leo.yan@linaro.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 759 Lines: 16 On Sat, Apr 02, 2016 at 12:38:37AM +0800, Leo Yan wrote: > When task is migrated from CPU_A to CPU_B, scheduler will decrease > the task's load/util from the task's cfs_rq and also add them into > migrated cfs_rq. But if kernel enables CONFIG_FAIR_GROUP_SCHED then this > cfs_rq is not the same one with cpu's cfs_rq. As a result, after task is > migrated to CPU_B, then CPU_A still have task's stale value for > load/util; on the other hand CPU_B also cannot reflect new load/util > which introduced by the task. > > So this patch is to operate the task's load/util to cpu's cfs_rq, so > finally cpu's cfs_rq can really reflect task's migration. Sorry but that is unintelligible. What is the problem? Why do we care? How did you fix it? and at what cost?