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,DKIMWL_WL_HIGH, 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 BFC57C433B4 for ; Mon, 19 Apr 2021 20:24:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91FF461360 for ; Mon, 19 Apr 2021 20:24:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241924AbhDSUYa (ORCPT ); Mon, 19 Apr 2021 16:24:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37135 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231294AbhDSUY2 (ORCPT ); Mon, 19 Apr 2021 16:24:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618863838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qMK5LdGW1tcHxkX+kXlO6KoaSLfAhc06ukgjVccttxE=; b=VJceume/Gn75PSi39Z4vr3KIOCU/KEjx0I+tbzjyGnhCyQnMEK1QBMqOJjG1rkh3kna1v1 S4Ulcnr/tgvWD02IQyTsnS6gGQ9VBkWgB6NOl9FlXtv1Um/XFURTqw7LKYVvGqH7GnjEVk XJB3SnYcZxKntc2GXRBwec+XWeCQMog= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-391-QRMdvGKMNbqdW7a-UmQKQw-1; Mon, 19 Apr 2021 16:23:53 -0400 X-MC-Unique: QRMdvGKMNbqdW7a-UmQKQw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 86535801814; Mon, 19 Apr 2021 20:23:51 +0000 (UTC) Received: from lorien.usersys.redhat.com (unknown [10.22.8.218]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2C0DC5C1CF; Mon, 19 Apr 2021 20:23:50 +0000 (UTC) Date: Mon, 19 Apr 2021 16:23:48 -0400 From: Phil Auld To: Valentin Schneider 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 Message-ID: References: <20210415175846.494385-1-valentin.schneider@arm.com> <20210415175846.494385-3-valentin.schneider@arm.com> <87tuo6lg39.mognet@arm.com> <878s5ekxc4.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878s5ekxc4.mognet@arm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 19, 2021 at 06:17:47PM +0100 Valentin Schneider wrote: > 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: > Fair enough, my bad, the migration part immediately drew me to migrate_degrades_capacity(). > 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?" > prefer_no_migrate? Cheers, Phil --