From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751442AbeERMTV (ORCPT ); Fri, 18 May 2018 08:19:21 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:58302 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751112AbeERMTU (ORCPT ); Fri, 18 May 2018 08:19:20 -0400 Date: Fri, 18 May 2018 14:19:13 +0200 From: Peter Zijlstra To: Patrick Bellasi Cc: Vincent Guittot , mingo@kernel.org, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, yuyang.du@intel.com, pjt@google.com, bsegall@google.com, "Rafael J. Wysocki" Subject: Re: [PATCH v3] sched/fair: update scale invariance of PELT Message-ID: <20180518121913.GR12235@hirez.programming.kicks-ass.net> References: <1493389435-2525-1-git-send-email-vincent.guittot@linaro.org> <20180518093638.GL12198@hirez.programming.kicks-ass.net> <20180518101738.GM30654@e110439-lin> <20180518120851.GM12198@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180518120851.GM12198@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 18, 2018 at 02:08:51PM +0200, Peter Zijlstra wrote: > However, I think we can shrink util_avg unconditionally, which would > give us exactly the 4 byte hole we need. There is of course the problem that we track rq util_avg as a straight sum of entity util_avg, such that if you migrate/wake a bunch of tasks into the rq the sum can exceed the natural bounds, although it will settle down back to it. If we're really worried we could try and detect overflows on the summing and clip.