From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932236AbbJMIKa (ORCPT ); Tue, 13 Oct 2015 04:10:30 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43487 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932072AbbJMIKZ (ORCPT ); Tue, 13 Oct 2015 04:10:25 -0400 Date: Tue, 13 Oct 2015 10:10:23 +0200 From: Peter Zijlstra To: Yuyang Du Cc: Mike Galbraith , linux-kernel@vger.kernel.org Subject: Re: 4.3 group scheduling regression Message-ID: <20151013081023.GO11639@twins.programming.kicks-ass.net> References: <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> <20151013080648.GP3604@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151013080648.GP3604@twins.programming.kicks-ass.net> 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 10:06:48AM +0200, Peter Zijlstra wrote: > 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. That is, can you send the original patch with a Changelog etc.. so that I can press 'A' :-)