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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 7779CC43603 for ; Wed, 11 Dec 2019 16:44:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5064124653 for ; Wed, 11 Dec 2019 16:44:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730757AbfLKQoz (ORCPT ); Wed, 11 Dec 2019 11:44:55 -0500 Received: from foss.arm.com ([217.140.110.172]:38688 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730593AbfLKQol (ORCPT ); Wed, 11 Dec 2019 11:44:41 -0500 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 D616211B3; Wed, 11 Dec 2019 08:44:40 -0800 (PST) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id F1ED33F52E; Wed, 11 Dec 2019 08:44:39 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com Subject: [RFC PATCH 6/7] sched/fair: Split select_task_rq_fair want_affine logic Date: Wed, 11 Dec 2019 16:44:00 +0000 Message-Id: <20191211164401.5013-7-valentin.schneider@arm.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191211164401.5013-1-valentin.schneider@arm.com> References: <20191211164401.5013-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The domain loop within select_task_rq_fair() depends on a few bits of input, namely the SD flag we're looking for and whether we want_affine. For !want_affine, the domain loop will walk up the hierarchy to reach the highest domain with both SD_LOAD_BALANCE and the requested sd_flag (SD_BALANCE_{WAKE, FORK, EXEC}) set. In other words, that's a call to highest_flags_domain() for these two flags. Note that this is a static information wrt a given SD hierarchy, so we can cache that - but that comes in a later patch to ease reviewing. For want_affine, we'll walk up the hierarchy to reach the first domain with SD_LOAD_BALANCE, SD_WAKE_AFFINE, and that spans the tasks's prev_cpu. We still save a pointer to the last visited domain that had the requested sd_flag set (and SD_LOAD_BALANCE), which means that if we fail to go through the affine condition (e.g. no domain had SD_WAKE_AFFINE) we'll use the same SD as we would have found if we had !want_affine. Split the domain loop in !want_affine and want_affine paths. As it is, this leads to two domain walks instead of a single one, but stay tuned for the next patch. Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 30e8d357a24f..ea875c7c82d7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6370,29 +6370,36 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) } rcu_read_lock(); + + sd = highest_flags_domain(cpu, sd_flag | SD_LOAD_BALANCE); + + /* + * If !want_affine, we just look for the highest domain where + * sd_flag is set. + */ + if (!want_affine) + goto scan; + + /* + * Otherwise we look for the lowest domain with SD_WAKE_AFFINE and that + * spans both 'cpu' and 'prev_cpu'. + */ for_each_domain(cpu, tmp) { if (!(tmp->flags & SD_LOAD_BALANCE)) break; - /* - * If both 'cpu' and 'prev_cpu' are part of this domain, - * cpu is a valid SD_WAKE_AFFINE target. - */ - if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && + if ((tmp->flags & SD_WAKE_AFFINE) && cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { if (cpu != prev_cpu) new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync); - sd = NULL; /* Prefer wake_affine over balance flags */ + /* Prefer wake_affine over SD lookup */ + sd = NULL; break; } - - if (tmp->flags & sd_flag) - sd = tmp; - else if (!want_affine) - break; } +scan: if (unlikely(sd)) { /* Slow path */ new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); -- 2.24.0