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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 00D00C433FE for ; Wed, 9 Dec 2020 11:33:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A078B23B40 for ; Wed, 9 Dec 2020 11:33:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730806AbgLILdy (ORCPT ); Wed, 9 Dec 2020 06:33:54 -0500 Received: from outbound-smtp15.blacknight.com ([46.22.139.232]:33277 "EHLO outbound-smtp15.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729988AbgLILdy (ORCPT ); Wed, 9 Dec 2020 06:33:54 -0500 Received: from mail.blacknight.com (pemlinmail02.blacknight.ie [81.17.254.11]) by outbound-smtp15.blacknight.com (Postfix) with ESMTPS id 93DE71C3E97 for ; Wed, 9 Dec 2020 11:33:02 +0000 (GMT) Received: (qmail 24101 invoked from network); 9 Dec 2020 11:33:02 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 9 Dec 2020 11:33:02 -0000 Date: Wed, 9 Dec 2020 11:33:00 +0000 From: Mel Gorman To: "Li, Aubrey" Cc: Vincent Guittot , Peter Ziljstra , Ingo Molnar , LKML , Barry Song , Juri Lelli , Valentin Schneider , Linux-ARM Subject: Re: [PATCH 2/4] sched/fair: Move avg_scan_cost calculations under SIS_PROP Message-ID: <20201209113300.GN3371@techsingularity.net> References: <20201208153501.1467-1-mgorman@techsingularity.net> <20201208153501.1467-3-mgorman@techsingularity.net> <3255625e-fa92-dc09-9fab-5621122f4af0@linux.intel.com> <20201209090507.GM3371@techsingularity.net> <14963d1e-02ea-c298-d6b4-2db637913ee3@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <14963d1e-02ea-c298-d6b4-2db637913ee3@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 09, 2020 at 07:07:11PM +0800, Li, Aubrey wrote: > On 2020/12/9 17:05, Mel Gorman wrote: > > On Wed, Dec 09, 2020 at 01:28:11PM +0800, Li, Aubrey wrote: > >>>> nr = div_u64(span_avg, avg_cost); > >>>> else > >>>> nr = 4; > >>>> - } > >>>> - > >>>> - time = cpu_clock(this); > >>>> > >>>> - cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > >>>> + time = cpu_clock(this); > >>>> + } > >>>> > >>>> for_each_cpu_wrap(cpu, cpus, target) { > >>>> if (!--nr) > >> > >> nr is the key of this throttling mechanism, need to be placed under sched_feat(SIS_PROP) as well. > >> > > > > It isn't necessary as nr in initialised to INT_MAX if !SIS_PROP. > >If !SIS_PROP, nr need to -1 then tested in the loop, instead of testing directly. > But with SIS_PROP, need adding a test in the loop. > Since SIS_PROP is default true, I think it's okay to keep the current way. > It's because it's default true and the cost is negligible that I'm leaving it alone. The branch cost and nr accounting cost is negligible and it avoids peppering select_idle_cpu() with too many SIS_PROP checks. -- Mel Gorman SUSE Labs