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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 081A3C4361B for ; Wed, 9 Dec 2020 14:54:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9CCF23406 for ; Wed, 9 Dec 2020 14:54:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733141AbgLIOy6 (ORCPT ); Wed, 9 Dec 2020 09:54:58 -0500 Received: from mga07.intel.com ([134.134.136.100]:36379 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732029AbgLIOy5 (ORCPT ); Wed, 9 Dec 2020 09:54:57 -0500 IronPort-SDR: EW0jMSuI88F72xHj3xEyz8VH8GAitO3LFpnY7xcrRjJPv4dy7ni2+Teyc+4dBp+p+sN1go4YFk ZdscerwY8A4w== X-IronPort-AV: E=McAfee;i="6000,8403,9829"; a="238190270" X-IronPort-AV: E=Sophos;i="5.78,405,1599548400"; d="scan'208";a="238190270" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Dec 2020 06:53:11 -0800 IronPort-SDR: 7YLB6sy+gCripowYjddwBifblNypo6dqMRXSad1apnV/i19d1OsqGNoRyvYf8eYnewDotGL6Zy NOgiTUrPC5aA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,405,1599548400"; d="scan'208";a="368212953" Received: from cli6-desk1.ccr.corp.intel.com (HELO [10.239.161.125]) ([10.239.161.125]) by fmsmga004.fm.intel.com with ESMTP; 09 Dec 2020 06:53:08 -0800 Subject: Re: [RFC PATCH v7] sched/fair: select idle cpu from idle cpumask for task wakeup To: Vincent Guittot Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Mel Gorman , Valentin Schneider , Qais Yousef , Dietmar Eggemann , Steven Rostedt , Ben Segall , Tim Chen , linux-kernel , Mel Gorman , Jiang Biao References: <20201209062404.175565-1-aubrey.li@linux.intel.com> <20201209081541.GA5071@vingu-book> <1e68b6fe-2f22-2fbd-3f6b-645994854918@linux.intel.com> From: "Li, Aubrey" Message-ID: Date: Wed, 9 Dec 2020 22:53:07 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/9 21:09, Vincent Guittot wrote: > On Wed, 9 Dec 2020 at 11:58, Li, Aubrey wrote: >> >> On 2020/12/9 16:15, Vincent Guittot wrote: >>> Le mercredi 09 déc. 2020 à 14:24:04 (+0800), Aubrey Li a écrit : >>>> Add idle cpumask to track idle cpus in sched domain. Every time >>>> a CPU enters idle, the CPU is set in idle cpumask to be a wakeup >>>> target. And if the CPU is not in idle, the CPU is cleared in idle >>>> cpumask during scheduler tick to ratelimit idle cpumask update. >>>> >>>> When a task wakes up to select an idle cpu, scanning idle cpumask >>>> has lower cost than scanning all the cpus in last level cache domain, >>>> especially when the system is heavily loaded. >>>> >>>> Benchmarks including hackbench, schbench, uperf, sysbench mysql >>>> and kbuild were tested on a x86 4 socket system with 24 cores per >>>> socket and 2 hyperthreads per core, total 192 CPUs, no regression >>>> found. >>>> >>>> v6->v7: >>>> - place the whole idle cpumask mechanism under CONFIG_SMP. >>>> >>>> v5->v6: >>>> - decouple idle cpumask update from stop_tick signal, set idle CPU >>>> in idle cpumask every time the CPU enters idle >>>> >>>> v4->v5: >>>> - add update_idle_cpumask for s2idle case >>>> - keep the same ordering of tick_nohz_idle_stop_tick() and update_ >>>> idle_cpumask() everywhere >>>> >>>> v3->v4: >>>> - change setting idle cpumask from every idle entry to tickless idle >>>> if cpu driver is available. >>>> - move clearing idle cpumask to scheduler_tick to decouple nohz mode. >>>> >>>> v2->v3: >>>> - change setting idle cpumask to every idle entry, otherwise schbench >>>> has a regression of 99th percentile latency. >>>> - change clearing idle cpumask to nohz_balancer_kick(), so updating >>>> idle cpumask is ratelimited in the idle exiting path. >>>> - set SCHED_IDLE cpu in idle cpumask to allow it as a wakeup target. >>>> >>>> v1->v2: >>>> - idle cpumask is updated in the nohz routines, by initializing idle >>>> cpumask with sched_domain_span(sd), nohz=off case remains the original >>>> behavior. >>>> >>>> Cc: Peter Zijlstra >>>> Cc: Mel Gorman >>>> Cc: Vincent Guittot >>>> Cc: Qais Yousef >>>> Cc: Valentin Schneider >>>> Cc: Jiang Biao >>>> Cc: Tim Chen >>>> Signed-off-by: Aubrey Li >>>> --- >>>> include/linux/sched/topology.h | 13 +++++++++ >>>> kernel/sched/core.c | 2 ++ >>>> kernel/sched/fair.c | 51 +++++++++++++++++++++++++++++++++- >>>> kernel/sched/idle.c | 5 ++++ >>>> kernel/sched/sched.h | 4 +++ >>>> kernel/sched/topology.c | 3 +- >>>> 6 files changed, 76 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h >>>> index 820511289857..b47b85163607 100644 >>>> --- a/include/linux/sched/topology.h >>>> +++ b/include/linux/sched/topology.h >>>> @@ -65,8 +65,21 @@ struct sched_domain_shared { >>>> atomic_t ref; >>>> atomic_t nr_busy_cpus; >>>> int has_idle_cores; >>>> + /* >>>> + * Span of all idle CPUs in this domain. >>>> + * >>>> + * NOTE: this field is variable length. (Allocated dynamically >>>> + * by attaching extra space to the end of the structure, >>>> + * depending on how many CPUs the kernel has booted up with) >>>> + */ >>>> + unsigned long idle_cpus_span[]; >>>> }; >>>> >>>> +static inline struct cpumask *sds_idle_cpus(struct sched_domain_shared *sds) >>>> +{ >>>> + return to_cpumask(sds->idle_cpus_span); >>>> +} >>>> + >>>> struct sched_domain { >>>> /* These fields must be setup */ >>>> struct sched_domain __rcu *parent; /* top domain must be null terminated */ >>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >>>> index c4da7e17b906..c4c51ff3402a 100644 >>>> --- a/kernel/sched/core.c >>>> +++ b/kernel/sched/core.c >>>> @@ -4011,6 +4011,7 @@ void scheduler_tick(void) >>>> >>>> #ifdef CONFIG_SMP >>>> rq->idle_balance = idle_cpu(cpu); >>>> + update_idle_cpumask(cpu, false); >>> >>> Test rq->idle_balance here instead of adding the test in update_idle_cpumask which is only >>> relevant for this situation. >> >> If called from idle path, because !set_idle is false, rq->idle_balance won't be tested actually. >> >> if (!set_idle && rq->idle_balance) >> return; >> >> So is it okay to leave it here to keep scheduler_tick a bit concise? > > I don't like having a tick specific condition in a generic function. > rq->idle_balance is only relevant in this case > > calling update_idle_cpumask(rq->idle_balance) in scheduler_tick() > should do the job and we can remove the check of rq->idle_balance in > update_idle_cpumask() > > In case of scheduler_tick() called when idle , we will only test if > (rq->last_idle_state == idle_state) and return > I see, will come up with a v8 soon. Thanks, -Aubrey