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 D4706C433ED for ; Mon, 19 Apr 2021 17:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7A21611F2 for ; Mon, 19 Apr 2021 17:17:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239687AbhDSRSX (ORCPT ); Mon, 19 Apr 2021 13:18:23 -0400 Received: from foss.arm.com ([217.140.110.172]:47076 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232572AbhDSRSV (ORCPT ); Mon, 19 Apr 2021 13:18:21 -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 8984C1478; Mon, 19 Apr 2021 10:17:51 -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 02DB53F7D7; Mon, 19 Apr 2021 10:17:49 -0700 (PDT) From: Valentin Schneider To: Phil Auld Cc: Rik van Riel , linux-kernel@vger.kernel.org, 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> <87tuo6lg39.mognet@arm.com> Date: Mon, 19 Apr 2021 18:17:47 +0100 Message-ID: <878s5ekxc4.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/04/21 08:59, Phil Auld wrote: > On Fri, Apr 16, 2021 at 10:43:38AM +0100 Valentin Schneider wrote: >> On 15/04/21 16:39, Rik van Riel wrote: >> > On Thu, 2021-04-15 at 18:58 +0100, Valentin Schneider wrote: >> >> @@ -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" ? > > I thought Rik meant tsk_cache_hot, for which I'd suggest at least > buying a vowel and putting an 'a' in there :) > That's the one I was eyeing: s/tsk_cache_hot/migration_harmful/ or somesuch. Right now we're feeding it: o migrate_degrades_locality() o task_hot() and I'm adding another one, so that's 2/3 which don't actually care about cache hotness, but rather "does doing this migration degrade/improve $criterion?"