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=-15.7 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,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 B792EC433F5 for ; Fri, 17 Sep 2021 18:47:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 928F361241 for ; Fri, 17 Sep 2021 18:47:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343563AbhIQStA (ORCPT ); Fri, 17 Sep 2021 14:49:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39864 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242488AbhIQSs7 (ORCPT ); Fri, 17 Sep 2021 14:48:59 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4BE1C061574 for ; Fri, 17 Sep 2021 11:47:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=LHCw/WZExEGega1av8JENylG4x6TuzO3VNj5w/otKQk=; b=pvV3jZa3h3dBUduo85AtoocFKG +rA/dYtIJWCYsehoprs12lJWa+AbyNfzBI1Lu2eA3wagOs2bvDGXDbvWrHxyKYzI+5l9XGzuDPkZh hxXWNHJOHUPud4EzUhnNLkYhweuEjKptLLjQ49Pzlr8ppneTHwhtBJUlarUMd8agx10fbpIftfKAP XBOutNfaFRd0ozS3DgnE1Qtg+0zrvWit9L7vjo23A39hX7twXv5VMDFWouyCtBpLSn6ltHGBQa60T ljhdHIsOQd0B9mHctIwWhg4A7C1eahRBibLUqi+S+hCnLTBvbfZKiox5wBvJIkdHw84SKsLnHONP4 kq6ZJDmA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mRIt1-003vHw-Qu; Fri, 17 Sep 2021 18:47:00 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 7B8FE986246; Fri, 17 Sep 2021 20:46:59 +0200 (CEST) Date: Fri, 17 Sep 2021 20:46:59 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: Ricardo Neri , Ingo Molnar , Juri Lelli , Srikar Dronamraju , Nicholas Piggin , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Len Brown , Srinivas Pandruvada , Tim Chen , Aubrey Li , "Ravi V. Shankar" , Ricardo Neri , Quentin Perret , "Joel Fernandes (Google)" , linuxppc-dev@lists.ozlabs.org, linux-kernel , Aubrey Li , Daniel Bristot de Oliveira , "Rafael J . Wysocki" Subject: Re: [PATCH v5 6/6] sched/fair: Consider SMT in ASYM_PACKING load balance Message-ID: <20210917184659.GI4323@worktop.programming.kicks-ass.net> References: <20210911011819.12184-1-ricardo.neri-calderon@linux.intel.com> <20210911011819.12184-7-ricardo.neri-calderon@linux.intel.com> <20210917010044.GA23727@ranerica-svr.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 17, 2021 at 05:25:02PM +0200, Vincent Guittot wrote: > With the removal of the condition !sds->local_stat.sum_nr_running > which seems useless because dst_cpu is idle and not SMT, this patch > looks good to me I've made it look like this. Thanks! --- Subject: sched/fair: Consider SMT in ASYM_PACKING load balance From: Ricardo Neri Date: Fri, 10 Sep 2021 18:18:19 -0700 From: Ricardo Neri When deciding to pull tasks in ASYM_PACKING, it is necessary not only to check for the idle state of the destination CPU, dst_cpu, but also of its SMT siblings. If dst_cpu is idle but its SMT siblings are busy, performance suffers if it pulls tasks from a medium priority CPU that does not have SMT siblings. Implement asym_smt_can_pull_tasks() to inspect the state of the SMT siblings of both dst_cpu and the CPUs in the candidate busiest group. Signed-off-by: Ricardo Neri Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Joel Fernandes (Google) Reviewed-by: Len Brown Link: https://lkml.kernel.org/r/20210911011819.12184-7-ricardo.neri-calderon@linux.intel.com --- kernel/sched/fair.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8538,10 +8538,96 @@ group_type group_classify(unsigned int i return group_has_spare; } +/** + * asym_smt_can_pull_tasks - Check whether the load balancing CPU can pull tasks + * @dst_cpu: Destination CPU of the load balancing + * @sds: Load-balancing data with statistics of the local group + * @sgs: Load-balancing statistics of the candidate busiest group + * @sg: The candidate busiest group + * + * Check the state of the SMT siblings of both @sds::local and @sg and decide + * if @dst_cpu can pull tasks. + * + * If @dst_cpu does not have SMT siblings, it can pull tasks if two or more of + * the SMT siblings of @sg are busy. If only one CPU in @sg is busy, pull tasks + * only if @dst_cpu has higher priority. + * + * If both @dst_cpu and @sg have SMT siblings, and @sg has exactly one more + * busy CPU than @sds::local, let @dst_cpu pull tasks if it has higher priority. + * Bigger imbalances in the number of busy CPUs will be dealt with in + * update_sd_pick_busiest(). + * + * If @sg does not have SMT siblings, only pull tasks if all of the SMT siblings + * of @dst_cpu are idle and @sg has lower priority. + */ +static bool asym_smt_can_pull_tasks(int dst_cpu, struct sd_lb_stats *sds, + struct sg_lb_stats *sgs, + struct sched_group *sg) +{ +#ifdef CONFIG_SCHED_SMT + bool local_is_smt, sg_is_smt; + int sg_busy_cpus; + + local_is_smt = sds->local->flags & SD_SHARE_CPUCAPACITY; + sg_is_smt = sg->flags & SD_SHARE_CPUCAPACITY; + + sg_busy_cpus = sgs->group_weight - sgs->idle_cpus; + + if (!local_is_smt) { + /* + * If we are here, @dst_cpu is idle and does not have SMT + * siblings. Pull tasks if candidate group has two or more + * busy CPUs. + */ + if (sg_busy_cpus >= 2) /* implies sg_is_smt */ + return true; + + /* + * @dst_cpu does not have SMT siblings. @sg may have SMT + * siblings and only one is busy. In such case, @dst_cpu + * can help if it has higher priority and is idle (i.e., + * it has no running tasks). + */ + return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu); + } + + /* @dst_cpu has SMT siblings. */ + + if (sg_is_smt) { + int local_busy_cpus = sds->local->group_weight - + sds->local_stat.idle_cpus; + int busy_cpus_delta = sg_busy_cpus - local_busy_cpus; + + if (busy_cpus_delta == 1) + return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu); + + return false; + } + + /* + * @sg does not have SMT siblings. Ensure that @sds::local does not end + * up with more than one busy SMT sibling and only pull tasks if there + * are not busy CPUs (i.e., no CPU has running tasks). + */ + if (!sds->local_stat.sum_nr_running) + return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu); + + return false; +#else + /* Always return false so that callers deal with non-SMT cases. */ + return false; +#endif +} + static inline bool sched_asym(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *sgs, struct sched_group *group) { + /* Only do SMT checks if either local or candidate have SMT siblings */ + if ((sds->local->flags & SD_SHARE_CPUCAPACITY) || + (group->flags & SD_SHARE_CPUCAPACITY)) + return asym_smt_can_pull_tasks(env->dst_cpu, sds, sgs, group); + return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu); } @@ -9547,6 +9633,12 @@ static struct rq *find_busiest_queue(str nr_running == 1) continue; + /* Make sure we only pull tasks from a CPU of lower priority */ + if ((env->sd->flags & SD_ASYM_PACKING) && + sched_asym_prefer(i, env->dst_cpu) && + nr_running == 1) + continue; + switch (env->migration_type) { case migrate_load: /*