From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71502C43142 for ; Thu, 2 Aug 2018 13:03:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3127A2150D for ; Thu, 2 Aug 2018 13:03:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3127A2150D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732400AbeHBOyx (ORCPT ); Thu, 2 Aug 2018 10:54:53 -0400 Received: from foss.arm.com ([217.140.101.70]:57800 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732267AbeHBOyx (ORCPT ); Thu, 2 Aug 2018 10:54:53 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A53577A9; Thu, 2 Aug 2018 06:03:46 -0700 (PDT) Received: from queper01-lin (queper01-lin.emea.arm.com [10.4.13.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B08003F2EA; Thu, 2 Aug 2018 06:03:42 -0700 (PDT) Date: Thu, 2 Aug 2018 14:03:38 +0100 From: Quentin Perret To: Peter Zijlstra Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator Message-ID: <20180802130337.uf6tlac2hg4nkbwr@queper01-lin> References: <20180724122521.22109-1-quentin.perret@arm.com> <20180724122521.22109-10-quentin.perret@arm.com> <20180802122629.GU2476@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180802122629.GU2476@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 02 Aug 2018 at 14:26:29 (+0200), Peter Zijlstra wrote: > On Tue, Jul 24, 2018 at 01:25:16PM +0100, Quentin Perret wrote: > > @@ -5100,8 +5118,17 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) > > update_cfs_group(se); > > } > > > > - if (!se) > > + if (!se) { > > add_nr_running(rq, 1); > > + /* > > + * The utilization of a new task is 'wrong' so wait for it > > + * to build some utilization history before trying to detect > > + * the overutilized flag. > > + */ > > + if (flags & ENQUEUE_WAKEUP) > > + update_overutilized_status(rq); > > + > > + } > > > > hrtick_update(rq); > > } > > That is a somewhat dodgy hack. There is no guarantee what so ever that > when the task wakes next its history is any better. The comment doesn't > reflect this I feel. AFAICT the main use-case here is to avoid re-enabling the load balance and ruining all the task placement because of a tiny task. I don't really see how we can do that differently ... Or am I missing something Morten ? In the meantime, I can try to improve the comment at least :-) Thanks, Quentin