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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 572A2C433ED for ; Fri, 16 Apr 2021 09:43:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A7EF6115B for ; Fri, 16 Apr 2021 09:43:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242011AbhDPJoH (ORCPT ); Fri, 16 Apr 2021 05:44:07 -0400 Received: from foss.arm.com ([217.140.110.172]:37412 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235027AbhDPJoG (ORCPT ); Fri, 16 Apr 2021 05:44:06 -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 3AF21106F; Fri, 16 Apr 2021 02:43:42 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BCC153FA35; Fri, 16 Apr 2021 02:43:40 -0700 (PDT) From: Valentin Schneider To: Rik van Riel , linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Morten Rasmussen , Qais Yousef , Quentin Perret , Pavan Kondeti , Lingutla Chandrasekhar Subject: Re: [PATCH 2/2] sched/fair: Relax task_hot() for misfit tasks In-Reply-To: References: <20210415175846.494385-1-valentin.schneider@arm.com> <20210415175846.494385-3-valentin.schneider@arm.com> Date: Fri, 16 Apr 2021 10:43:38 +0100 Message-ID: <87tuo6lg39.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/04/21 16:39, Rik van Riel wrote: > On Thu, 2021-04-15 at 18:58 +0100, Valentin Schneider wrote: >> Consider the following topology: >> >> Long story short, preempted misfit tasks are affected by task_hot(), >> while >> currently running misfit tasks are intentionally preempted by the >> stopper >> task to migrate them over to a higher-capacity CPU. >> >> Align detach_tasks() with the active-balance logic and let it pick a >> cache-hot misfit task when the destination CPU can provide a capacity >> uplift. >> >> Signed-off-by: Valentin Schneider > > Reviewed-by: Rik van Riel > Thanks! > > This patch looks good, but... > >> @@ -7672,6 +7698,15 @@ int can_migrate_task(struct task_struct *p, >> struct lb_env *env) >> if (tsk_cache_hot == -1) >> tsk_cache_hot = task_hot(p, env); >> >> + /* >> + * On a (sane) asymmetric CPU capacity system, the increase in >> compute >> + * capacity should offset any potential performance hit caused >> by a >> + * migration. >> + */ >> + if ((env->dst_grp_type == group_has_spare) && >> + !migrate_degrades_capacity(p, env)) >> + tsk_cache_hot = 0; > > ... I'm starting to wonder if we should not rename the > tsk_cache_hot variable to something else to make this > code more readable. Probably in another patch :) > I'd tend to agree, but naming is hard. "migration_harmful" ? > -- > All Rights Reversed.