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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C9E5C3A5A7 for ; Thu, 8 Dec 2022 08:51:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230026AbiLHIvK (ORCPT ); Thu, 8 Dec 2022 03:51:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229937AbiLHIvH (ORCPT ); Thu, 8 Dec 2022 03:51:07 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id F0761CDC; Thu, 8 Dec 2022 00:51:05 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 67575D6E; Thu, 8 Dec 2022 00:51:12 -0800 (PST) Received: from localhost (ionvoi01-desktop.cambridge.arm.com [10.1.196.65]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4806B3F73D; Thu, 8 Dec 2022 00:51:05 -0800 (PST) Date: Thu, 8 Dec 2022 08:51:03 +0000 From: Ionela Voinescu To: Ricardo Neri Cc: "Peter Zijlstra (Intel)" , Juri Lelli , Vincent Guittot , Ricardo Neri , "Ravi V. Shankar" , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Len Brown , Mel Gorman , "Rafael J. Wysocki" , Srinivas Pandruvada , Steven Rostedt , Tim Chen , Valentin Schneider , x86@kernel.org, "Joel Fernandes (Google)" , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "Tim C . Chen" Subject: Re: [PATCH v2 09/22] sched/fair: Use IPC class score to select a busiest runqueue Message-ID: References: <20221128132100.30253-1-ricardo.neri-calderon@linux.intel.com> <20221128132100.30253-10-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221128132100.30253-10-ricardo.neri-calderon@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Monday 28 Nov 2022 at 05:20:47 (-0800), Ricardo Neri wrote: > For two runqueues of equal priority and equal number of running of tasks, > select the one whose current task would have the highest IPC class score > if placed on the destination CPU. > [..] > +static int ipcc_score_delta(struct task_struct *p, int alt_cpu) > +{ > + unsigned long ipcc = p->ipcc; > + > + if (!sched_ipcc_enabled()) > + return INT_MIN; > + > + return arch_get_ipcc_score(ipcc, alt_cpu) - > + arch_get_ipcc_score(ipcc, task_cpu(p)); Nit: arch_get_ipcc_score() return values are never checked for error. > +} > + > #else /* CONFIG_IPC_CLASSES */ > static void update_sg_lb_ipcc_stats(struct sg_lb_ipcc_stats *sgcs, > struct rq *rq) > @@ -9258,6 +9276,11 @@ static bool sched_asym_ipcc_pick(struct sched_group *a, > return false; > } > > +static int ipcc_score_delta(struct task_struct *p, int alt_cpu) > +{ > + return INT_MIN; > +} > + > #endif /* CONFIG_IPC_CLASSES */ > > /** > @@ -10419,8 +10442,8 @@ static struct rq *find_busiest_queue(struct lb_env *env, > { > struct rq *busiest = NULL, *rq; > unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1; > + int i, busiest_ipcc_delta = INT_MIN; > unsigned int busiest_nr = 0; > - int i; > > for_each_cpu_and(i, sched_group_span(group), env->cpus) { > unsigned long capacity, load, util; > @@ -10526,8 +10549,37 @@ static struct rq *find_busiest_queue(struct lb_env *env, > > case migrate_task: > if (busiest_nr < nr_running) { > + struct task_struct *curr; > + > busiest_nr = nr_running; > busiest = rq; > + > + /* > + * Remember the IPC score delta of busiest::curr. > + * We may need it to break a tie with other queues > + * with equal nr_running. > + */ > + curr = rcu_dereference(busiest->curr); > + busiest_ipcc_delta = ipcc_score_delta(curr, > + env->dst_cpu); > + /* > + * If rq and busiest have the same number of running > + * tasks, pick rq if doing so would give rq::curr a > + * bigger IPC boost on dst_cpu. > + */ > + } else if (sched_ipcc_enabled() && > + busiest_nr == nr_running) { > + struct task_struct *curr; > + int delta; > + > + curr = rcu_dereference(rq->curr); > + delta = ipcc_score_delta(curr, env->dst_cpu); > + > + if (busiest_ipcc_delta < delta) { > + busiest_ipcc_delta = delta; > + busiest_nr = nr_running; > + busiest = rq; > + } > } > break; > While in the commit message you describe this as breaking a tie for asym_packing, the code here does not only affect asym_packing. If another architecture would have sched_ipcc_enabled() it would use this as generic policy, and that might not be desired. Hope it helps, Ionela. > -- > 2.25.1 > >