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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,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 278B2C433ED for ; Fri, 9 Apr 2021 16:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBDA461041 for ; Fri, 9 Apr 2021 16:14:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233599AbhDIQOt (ORCPT ); Fri, 9 Apr 2021 12:14:49 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:51570 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231946AbhDIQOq (ORCPT ); Fri, 9 Apr 2021 12:14:46 -0400 Date: Fri, 09 Apr 2021 16:14:31 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1617984872; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ul0uzH2FQLFVHfSBRCinHJEz1JT+AehwcswM1KXNt+A=; b=YumX72Q1lt6M1YOwylzWqRkx6OyiE+h0RPTUoEa2O+I7FaTUO3bs9enq4jgNIZMON8+dUb S0iu6kPcPOgmARZzyPIB+W3ouqICQ7KQZFFG5ZjscvbaTIv2ZH39D//iKchmFnPbmyP0g/ IJsyCEElR2n/3gPe33S+5yIdmnsylNl7aEX8mby4F6hUDq7r5KlOMtB4S51Q2IvV0LbsT9 +8dCrKSH0Q73bXXzLkf+x8wDChUzZjN7gwvM8n9H5WUMoBkHX7d5Roz3CobD201WaqhYca XJC7c9JEermdK6kGjCwhNA7dF8bkweGWc2a38JYgveULVAYxxCohErCWtbRVlQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1617984872; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ul0uzH2FQLFVHfSBRCinHJEz1JT+AehwcswM1KXNt+A=; b=uAwHwbJYw4sPhNk5gwvr4VZLa2MFtW8hOmvFb0DdRUyme6z+Y0MsBeit/6oYFppGjw0iXQ A7ZU/PjlkwNkdNCA== From: "tip-bot2 for Valentin Schneider" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Clean up active balance nr_balance_failed trickery Cc: Valentin Schneider , "Peter Zijlstra (Intel)" , Dietmar Eggemann , Vincent Guittot , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210407220628.3798191-3-valentin.schneider@arm.com> References: <20210407220628.3798191-3-valentin.schneider@arm.com> MIME-Version: 1.0 Message-ID: <161798487149.29796.18250747063112261212.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 23fb06d9602b0fcfa1a16357a5d7a7f7076a39e2 Gitweb: https://git.kernel.org/tip/23fb06d9602b0fcfa1a16357a5d7a7f7076a39e2 Author: Valentin Schneider AuthorDate: Wed, 07 Apr 2021 23:06:27 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 09 Apr 2021 18:02:20 +02:00 sched/fair: Clean up active balance nr_balance_failed trickery 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. Cleanup the LBF_DST_PINNED active balance special case. Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Reviewed-by: Vincent Guittot Link: https://lkml.kernel.org/r/20210407220628.3798191-3-valentin.schneider@arm.com --- kernel/sched/fair.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1ad929b..356637a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7453,6 +7453,7 @@ 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; @@ -7614,10 +7615,13 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) * our sched_group. We may want to revisit it if we couldn't * meet load balance goals by pulling other tasks on src_cpu. * - * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have - * already computed one in current iteration. + * Avoid computing new_dst_cpu + * - for NEWLY_IDLE + * - if we have already computed one in current iteration + * - if it's an active balance */ - if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED)) + if (env->idle == CPU_NEWLY_IDLE || + env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB)) return 0; /* Prevent to re-select dst_cpu via env's CPUs: */ @@ -7642,10 +7646,14 @@ 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); @@ -9836,9 +9844,6 @@ more_balance: 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; @@ -9988,13 +9993,7 @@ static int active_load_balance_cpu_stop(void *data) .src_cpu = busiest_rq->cpu, .src_rq = busiest_rq, .idle = CPU_IDLE, - /* - * can_migrate_task() doesn't need to compute new_dst_cpu - * for active balancing. Since we have CPU_IDLE, but no - * @dst_grpmask we need to make that test go away with lying - * about DST_PINNED. - */ - .flags = LBF_DST_PINNED, + .flags = LBF_ACTIVE_LB, }; schedstat_inc(sd->alb_count);