From patchwork Sat Sep 11 01:18:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ricardo Neri X-Patchwork-Id: 1526671 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=2404:9400:2:0:216:3eff:fee1:b9f1; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2404:9400:2:0:216:3eff:fee1:b9f1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4H5w3Z2ZBgz9sVw for ; Sat, 11 Sep 2021 11:23:06 +1000 (AEST) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4H5w3Z1gNCz2yp5 for ; Sat, 11 Sep 2021 11:23:06 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.intel.com (client-ip=134.134.136.65; helo=mga03.intel.com; envelope-from=ricardo.neri-calderon@linux.intel.com; receiver=) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4H5w0L4RbKz2yHj for ; Sat, 11 Sep 2021 11:20:18 +1000 (AEST) X-IronPort-AV: E=McAfee;i="6200,9189,10103"; a="221271944" X-IronPort-AV: E=Sophos;i="5.85,284,1624345200"; d="scan'208";a="221271944" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Sep 2021 18:19:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,284,1624345200"; d="scan'208";a="695261645" Received: from ranerica-svr.sc.intel.com ([172.25.110.23]) by fmsmga006.fm.intel.com with ESMTP; 10 Sep 2021 18:19:08 -0700 From: Ricardo Neri To: "Peter Zijlstra (Intel)" , Ingo Molnar , Juri Lelli , Vincent Guittot Subject: [PATCH v5 6/6] sched/fair: Consider SMT in ASYM_PACKING load balance Date: Fri, 10 Sep 2021 18:18:19 -0700 Message-Id: <20210911011819.12184-7-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210911011819.12184-1-ricardo.neri-calderon@linux.intel.com> References: <20210911011819.12184-1-ricardo.neri-calderon@linux.intel.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Len Brown , Aubrey Li , "Rafael J . Wysocki" , Srikar Dronamraju , "Ravi V. Shankar" , linuxppc-dev@lists.ozlabs.org, Aubrey Li , Nicholas Piggin , Ricardo Neri , Steven Rostedt , Quentin Perret , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Srinivas Pandruvada , "Joel Fernandes \(Google\)" , Tim Chen , Dietmar Eggemann , linux-kernel@vger.kernel.org, Ricardo Neri Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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. Cc: Aubrey Li Cc: Ben Segall Cc: Daniel Bristot de Oliveira Cc: Dietmar Eggemann Cc: Mel Gorman Cc: Quentin Perret Cc: Rafael J. Wysocki Cc: Srinivas Pandruvada Cc: Steven Rostedt Cc: Tim Chen Reviewed-by: Joel Fernandes (Google) Reviewed-by: Len Brown Signed-off-by: Ricardo Neri Signed-off-by: Ricardo Neri Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Joel Fernandes (Google) Reviewed-by: Len Brown Reviewed-by: Vincent Guittot --- Changes since v4: * Use sg_lb_stats::sum_nr_running the idle state of a scheduling group. (Vincent, Peter) * Do not even idle CPUs in asym_smt_can_pull_tasks(). (Vincent) * Updated function documentation and corrected a typo. Changes since v3: * Removed the arch_asym_check_smt_siblings() hook. Discussions with the powerpc folks showed that this patch should not impact them. Also, more recent powerpc processor no longer use asym_packing. (PeterZ) * Removed unnecessary local variable in asym_can_pull_tasks(). (Dietmar) * Removed unnecessary check for local CPUs when the local group has zero utilization. (Joel) * Renamed asym_can_pull_tasks() as asym_smt_can_pull_tasks() to reflect the fact that it deals with SMT cases. * Made asym_smt_can_pull_tasks() return false for !CONFIG_SCHED_SMT so that callers can deal with non-SMT cases. Changes since v2: * Reworded the commit message to reflect updates in code. * Corrected misrepresentation of dst_cpu as the CPU doing the load balancing. (PeterZ) * Removed call to arch_asym_check_smt_siblings() as it is now called in sched_asym(). Changes since v1: * Don't bailout in update_sd_pick_busiest() if dst_cpu cannot pull tasks. Instead, reclassify the candidate busiest group, as it may still be selected. (PeterZ) * Avoid an expensive and unnecessary call to cpumask_weight() when determining if a sched_group is comprised of SMT siblings. (PeterZ). --- kernel/sched/fair.c | 94 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 26db017c14a3..8d763dd0174b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8597,10 +8597,98 @@ group_type group_classify(unsigned int imbalance_pct, 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_is_smt && sg_busy_cpus >= 2) + 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 !sds->local_stat.sum_nr_running && + 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); } @@ -9606,6 +9694,12 @@ static struct rq *find_busiest_queue(struct lb_env *env, 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: /*