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=-8.8 required=3.0 tests=BAYES_00, 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 96B1BC433B4 for ; Thu, 22 Apr 2021 19:19:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5525F613F5 for ; Thu, 22 Apr 2021 19:19:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238917AbhDVTUN (ORCPT ); Thu, 22 Apr 2021 15:20:13 -0400 Received: from foss.arm.com ([217.140.110.172]:55162 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236665AbhDVTUM (ORCPT ); Thu, 22 Apr 2021 15:20:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DE2B811D4; Thu, 22 Apr 2021 12:19:36 -0700 (PDT) Received: from e113632-lin (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 702183F694; Thu, 22 Apr 2021 12:19:35 -0700 (PDT) From: Valentin Schneider To: Dietmar Eggemann , linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Morten Rasmussen , Qais Yousef , Quentin Perret , Pavan Kondeti , Rik van Riel , Lingutla Chandrasekhar Subject: Re: [PATCH 1/2] sched/fair: Filter out locally-unsolvable misfit imbalances In-Reply-To: <519f7b86-851b-24f7-39aa-4bbdce5c7cd3@arm.com> References: <20210415175846.494385-1-valentin.schneider@arm.com> <20210415175846.494385-2-valentin.schneider@arm.com> <519f7b86-851b-24f7-39aa-4bbdce5c7cd3@arm.com> Date: Thu, 22 Apr 2021 20:19:30 +0100 Message-ID: <87r1j2t9dp.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/04/21 11:48, Dietmar Eggemann wrote: > On 15/04/2021 19:58, Valentin Schneider wrote: > > [...] > >> Aggregate a misfit task's load into sgs->group_misfit_task_load only if >> env->dst_cpu would grant it a capacity uplift. >> >> Note that the aforementioned capacity vs sgc->max_capacity comparison was >> meant to prevent misfit task downmigration: candidate groups classified as >> group_misfit_task but with a higher (max) CPU capacity than the destination CPU >> would be discarded. This change makes it so said group_misfit_task >> classification can't happen anymore, which may cause some undesired >> downmigrations. >> >> Further tweak find_busiest_queue() to ensure this doesn't happen. > > Maybe you can describe shortly here what's the new mechanism is you > replace the old 'prevent misfit task downmigration' with. > Will do. > Also note >> find_busiest_queue() can now iterate over CPUs with a higher capacity than >> the local CPU's, so add a capacity check there. > > [...] > >> +static inline void update_sg_lb_misfit_stats(struct lb_env *env, >> + struct sched_group *group, > > Seems to be not used. > Right, that's an update_sg_lb_stats() copy/paste fail :-) > >> @@ -9288,6 +9310,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env) >> if (!sds.busiest) >> goto out_balanced; >> >> + env->src_grp_type = busiest->group_type; > > Maybe a short comment why you set it here in fbg(). It's only used later > in fbq() for asym. CPU capacity sd but is set unconditionally. > Seeing as almost every other line there has an accompanying comment, I think I'll do that. > [...]