From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932083AbbJMIG7 (ORCPT ); Tue, 13 Oct 2015 04:06:59 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43287 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752568AbbJMIGx (ORCPT ); Tue, 13 Oct 2015 04:06:53 -0400 Date: Tue, 13 Oct 2015 10:06:48 +0200 From: Peter Zijlstra To: Yuyang Du Cc: Mike Galbraith , linux-kernel@vger.kernel.org Subject: Re: 4.3 group scheduling regression Message-ID: <20151013080648.GP3604@twins.programming.kicks-ass.net> References: <1444530318.3363.40.camel@gmail.com> <1444585321.4169.18.camel@gmail.com> <20151012072344.GM3604@twins.programming.kicks-ass.net> <1444635897.3425.19.camel@gmail.com> <20151012080407.GJ3816@twins.programming.kicks-ass.net> <20151012005351.GJ11102@intel.com> <20151012091206.GK3816@twins.programming.kicks-ass.net> <20151012021230.GK11102@intel.com> <1444645411.3534.5.camel@gmail.com> <20151012195516.GM11102@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151012195516.GM11102@intel.com> 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 On Tue, Oct 13, 2015 at 03:55:17AM +0800, Yuyang Du wrote: > I think maybe the real disease is the tg->load_avg is not updated in time. > I.e., it is after migrate, the source cfs_rq does not decrease its contribution > to the parent's tg->load_avg fast enough. No, using the load_avg for shares calculation seems wrong; that would mean we'd first have to ramp up the avg before you react. You want to react quickly to actual load changes, esp. going up. We use the avg to guess the global group load, since that's the best compromise we have, but locally it doesn't make sense to use the avg if we have the actual values.