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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A9756C5519F for ; Fri, 20 Nov 2020 08:57:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EC4122256 for ; Fri, 20 Nov 2020 08:57:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tBb/H8lh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727446AbgKTI5D (ORCPT ); Fri, 20 Nov 2020 03:57:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727160AbgKTI5C (ORCPT ); Fri, 20 Nov 2020 03:57:02 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52AF7C0613CF for ; Fri, 20 Nov 2020 00:57:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=lFHxzgab5fio/KXrJQrfE454z4bsCaBUVcUqkcbYglQ=; b=tBb/H8lhrultIR/T8/Zu1OmLW8 /zd8gfzND8C4vWVFJhyoEIWdhl1QGSzpj6IroRfQ780ZDXwY2JEnbmRI//R5r3iV96ySt6JthVuTe SCpiUAVhXA0H7GERqHYX2NmWRphzF7NrQPiR1YtuwBtEq91uQHv2p9V9Jboob7xUf1WPJ4MOoqXbr ahyBDWnhpYIqsB7ilUO+NcOUMhutrll8Q8oxSis1VrAqGSgbJNdsu3JB/ayzEQJhOrK0ZByoVvosU ntNYmx2aRmw/2TnOcBreIKRay4k/nazg1ZJgd6jyUDKvLJHoJ2UzvOsuZa3RJwI6xrmrbmUemHMZy O1MVNyuA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg2Dv-0002rU-7v; Fri, 20 Nov 2020 08:56:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DBF20304D28; Fri, 20 Nov 2020 09:56:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A706A29E75A18; Fri, 20 Nov 2020 09:56:53 +0100 (CET) Date: Fri, 20 Nov 2020 09:56:53 +0100 From: Peter Zijlstra To: "Rafael J. Wysocki" , Ingo Molnar Cc: Thomas Gleixner , Vincent Guittot , Morten Rasmussen , dietmar.eggemann@arm.com, patrick.bellasi@matbug.net, lenb@kernel.org, linux-kernel@vger.kernel.org, valentin.schneider@arm.com, ionela.voinescu@arm.com, qperret@google.com, viresh.kumar@linaro.org Subject: Re: [RFC] Documentation/scheduler/schedutil.txt Message-ID: <20201120085653.GA3092@hirez.programming.kicks-ass.net> References: <20201120075527.GB2414@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120075527.GB2414@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 20, 2020 at 08:55:27AM +0100, Peter Zijlstra wrote: > - In saturated scenarios task movement will cause some transient dips, > suppose we have a CPU saturated with 4 tasks, then when we migrate a task > to an idle CPU, the old CPU will have a 'running' value of 0.75 while the > new CPU will gain 0.25. This is inevitable and time progression will > correct this. XXX do we still guarantee f_max due to no idle-time? Do we want something like this? Is the 1.5 threshold sane? (it's been too long since I looked at actual numbers here) --- diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 68d369cba9e4..f0bed8902c40 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -90,3 +90,4 @@ SCHED_FEAT(WA_BIAS, true) */ SCHED_FEAT(UTIL_EST, true) SCHED_FEAT(UTIL_EST_FASTUP, true) +SCHED_FEAT(UTIL_SAT, true) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 590e6f27068c..bf70e5ed8ba6 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2593,10 +2593,17 @@ static inline unsigned long cpu_util_dl(struct rq *rq) return READ_ONCE(rq->avg_dl.util_avg); } +#define RUNNABLE_SAT (SCHED_CAPACITY_SCALE + SCHED_CAPACITY_SCALE/2) + static inline unsigned long cpu_util_cfs(struct rq *rq) { unsigned long util = READ_ONCE(rq->cfs.avg.util_avg); + if (sched_feat(UTIL_SAT)) { + if (READ_ONCE(rq->cfs.avg.runnable_avg) > RUNNABLE_SAT) + return SCHED_CAPACITY_SCALE; + } + if (sched_feat(UTIL_EST)) { util = max_t(unsigned long, util, READ_ONCE(rq->cfs.avg.util_est.enqueued));