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=-16.8 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,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 6CE64C433E6 for ; Thu, 11 Mar 2021 12:06:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A6B864FC0 for ; Thu, 11 Mar 2021 12:06:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233043AbhCKMGF (ORCPT ); Thu, 11 Mar 2021 07:06:05 -0500 Received: from foss.arm.com ([217.140.110.172]:34036 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232782AbhCKMFj (ORCPT ); Thu, 11 Mar 2021 07:05:39 -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 E7B131063; Thu, 11 Mar 2021 04:05:38 -0800 (PST) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 5D7C13F793; Thu, 11 Mar 2021 04:05:37 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Morten Rasmussen , Qais Yousef , Quentin Perret , Pavan Kondeti , Rik van Riel , Lingutla Chandrasekhar Subject: [PATCH v3 2/7] sched/fair: Clean up active balance nr_balance_failed trickery Date: Thu, 11 Mar 2021 12:05:22 +0000 Message-Id: <20210311120527.167870-3-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210311120527.167870-1-valentin.schneider@arm.com> References: <20210311120527.167870-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When triggering an active load balance, sd->nr_balance_failed is set to such a value that any further can_migrate_task() using said sd will ignore the output of task_hot(). This behaviour makes sense, as active load balance intentionally preempts a rq's running task to migrate it right away, but this asynchronous write is a bit shoddy, as the stopper thread might run active_load_balance_cpu_stop before the sd->nr_balance_failed write either becomes visible to the stopper's CPU or even happens on the CPU that appended the stopper work. Add a struct lb_env flag to denote active balancing, and use it in can_migrate_task(). Remove the sd->nr_balance_failed write that served the same purpose. Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 83aea97fbf22..f50a902bdf24 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7420,6 +7420,7 @@ enum migration_type { #define LBF_NEED_BREAK 0x02 #define LBF_DST_PINNED 0x04 #define LBF_SOME_PINNED 0x08 +#define LBF_ACTIVE_LB 0x10 struct lb_env { struct sched_domain *sd; @@ -7609,10 +7610,14 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) /* * Aggressive migration if: - * 1) destination numa is preferred - * 2) task is cache cold, or - * 3) too many balance attempts have failed. + * 1) active balance + * 2) destination numa is preferred + * 3) task is cache cold, or + * 4) too many balance attempts have failed. */ + if (env->flags & LBF_ACTIVE_LB) + return 1; + tsk_cache_hot = migrate_degrades_locality(p, env); if (tsk_cache_hot == -1) tsk_cache_hot = task_hot(p, env); @@ -9794,9 +9799,6 @@ static int load_balance(int this_cpu, struct rq *this_rq, active_load_balance_cpu_stop, busiest, &busiest->active_balance_work); } - - /* We've kicked active balancing, force task migration. */ - sd->nr_balance_failed = sd->cache_nice_tries+1; } } else { sd->nr_balance_failed = 0; @@ -9952,7 +9954,8 @@ static int active_load_balance_cpu_stop(void *data) * @dst_grpmask we need to make that test go away with lying * about DST_PINNED. */ - .flags = LBF_DST_PINNED, + .flags = LBF_DST_PINNED | + LBF_ACTIVE_LB, }; schedstat_inc(sd->alb_count); -- 2.25.1