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=-20.7 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 31CBCC4360C for ; Tue, 2 Mar 2021 09:35:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15AC76148E for ; Tue, 2 Mar 2021 09:35:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1382385AbhCBJZi (ORCPT ); Tue, 2 Mar 2021 04:25:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378857AbhCBJDa (ORCPT ); Tue, 2 Mar 2021 04:03:30 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEC11C0617A9; Tue, 2 Mar 2021 01:01:58 -0800 (PST) Date: Tue, 02 Mar 2021 09:01:55 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614675716; 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=gL2L6mzB88JT9RgI7oNm8yR02xN4CGy+373opBtjD0A=; b=sgX7aRna8p6A33gDu+Rn1AzbQP6CuNUoA5EL4VoqKk3so2FwhuQgIqdO7Y57b7kdVtmKxH a5eZBq+WQGZM/9Q99xctxIA1WDVw3cekKC062k4DW21mqbW/52sY0/1v/tUyFQmF0QMQdq uu5TFoixWHzEFa/Ei9yrjNmKvhqrMfHzbNompFRtlVItduKp3N1Q7IZ5ymmuy8leXmyTWP iAPXP0pQjxHLQE7tSnOqcmhF6fUiHQBbL0yEamDzTPHRzKXcbawjJHaOcO4c9WJ9rQw1+I bqRLrjY4MgaYLipfYXWeRS1/eceeK9ptU3AlgnvE/8HguwQydQHkkLdoi5iHUA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614675716; 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=gL2L6mzB88JT9RgI7oNm8yR02xN4CGy+373opBtjD0A=; b=lBn/NQJcj8kxjXgV73skej0sENNZGAAw8EMGmdQKpdfF9hnpWW/XOob3r7EBqJuVPva07H fv3obsNFbVQ/DDBw== From: "tip-bot2 for Vincent Guittot" 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: Remove update of blocked load from newidle_balance Cc: Vincent Guittot , "Peter Zijlstra (Intel)" , Valentin Schneider , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210224133007.28644-2-vincent.guittot@linaro.org> References: <20210224133007.28644-2-vincent.guittot@linaro.org> MIME-Version: 1.0 Message-ID: <161467571597.20312.15461052399950119430.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: 06a35afe89800789fc47ca5c41fbe435cc77d8e0 Gitweb: https://git.kernel.org/tip/06a35afe89800789fc47ca5c41fbe435cc77d8e0 Author: Vincent Guittot AuthorDate: Wed, 24 Feb 2021 14:30:01 +01:00 Committer: Peter Zijlstra CommitterDate: Mon, 01 Mar 2021 18:17:23 +01:00 sched/fair: Remove update of blocked load from newidle_balance newidle_balance runs with both preempt and irq disabled which prevent local irq to run during this period. The duration for updating the blocked load of CPUs varies according to the number of CPU cgroups with non-decayed load and extends this critical period to an uncontrolled level. Remove the update from newidle_balance and trigger a normal ILB that will take care of the update instead. This reduces the IRQ latency from O(nr_cgroups * nr_nohz_cpus) to O(nr_cgroups). Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210224133007.28644-2-vincent.guittot@linaro.org --- kernel/sched/fair.c | 33 +++++---------------------------- 1 file changed, 5 insertions(+), 28 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 794c2cb..806e16f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7392,8 +7392,6 @@ enum migration_type { #define LBF_NEED_BREAK 0x02 #define LBF_DST_PINNED 0x04 #define LBF_SOME_PINNED 0x08 -#define LBF_NOHZ_STATS 0x10 -#define LBF_NOHZ_AGAIN 0x20 struct lb_env { struct sched_domain *sd; @@ -8397,9 +8395,6 @@ static inline void update_sg_lb_stats(struct lb_env *env, for_each_cpu_and(i, sched_group_span(group), env->cpus) { struct rq *rq = cpu_rq(i); - if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false)) - env->flags |= LBF_NOHZ_AGAIN; - sgs->group_load += cpu_load(rq); sgs->group_util += cpu_util(i); sgs->group_runnable += cpu_runnable(rq); @@ -8940,11 +8935,6 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd struct sg_lb_stats tmp_sgs; int sg_status = 0; -#ifdef CONFIG_NO_HZ_COMMON - if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked)) - env->flags |= LBF_NOHZ_STATS; -#endif - do { struct sg_lb_stats *sgs = &tmp_sgs; int local_group; @@ -8981,14 +8971,6 @@ next_group: /* Tag domain that child domain prefers tasks go to siblings first */ sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING; -#ifdef CONFIG_NO_HZ_COMMON - if ((env->flags & LBF_NOHZ_AGAIN) && - cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) { - - WRITE_ONCE(nohz.next_blocked, - jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD)); - } -#endif if (env->sd->flags & SD_NUMA) env->fbq_type = fbq_classify_group(&sds->busiest_stat); @@ -10517,16 +10499,11 @@ static void nohz_newidle_balance(struct rq *this_rq) time_before(jiffies, READ_ONCE(nohz.next_blocked))) return; - raw_spin_unlock(&this_rq->lock); /* - * This CPU is going to be idle and blocked load of idle CPUs - * need to be updated. Run the ilb locally as it is a good - * candidate for ilb instead of waking up another idle CPU. - * Kick an normal ilb if we failed to do the update. + * Blocked load of idle CPUs need to be updated. + * Kick an ILB to update statistics. */ - if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE)) - kick_ilb(NOHZ_STATS_KICK); - raw_spin_lock(&this_rq->lock); + kick_ilb(NOHZ_STATS_KICK); } #else /* !CONFIG_NO_HZ_COMMON */ @@ -10587,8 +10564,6 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) update_next_balance(sd, &next_balance); rcu_read_unlock(); - nohz_newidle_balance(this_rq); - goto out; } @@ -10654,6 +10629,8 @@ out: if (pulled_task) this_rq->idle_stamp = 0; + else + nohz_newidle_balance(this_rq); rq_repin_lock(this_rq, rf);