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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6B298C34026 for ; Tue, 18 Feb 2020 17:27:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A2F120801 for ; Tue, 18 Feb 2020 17:27:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726841AbgBRR1v (ORCPT ); Tue, 18 Feb 2020 12:27:51 -0500 Received: from foss.arm.com ([217.140.110.172]:56790 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726475AbgBRR1u (ORCPT ); Tue, 18 Feb 2020 12:27:50 -0500 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 706AD31B; Tue, 18 Feb 2020 09:27:50 -0800 (PST) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.195.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1EBD03F703; Tue, 18 Feb 2020 09:27:49 -0800 (PST) Date: Tue, 18 Feb 2020 17:27:46 +0000 From: Qais Yousef To: Steven Rostedt Cc: Dietmar Eggemann , Ingo Molnar , Peter Zijlstra , Pavan Kondeti , Juri Lelli , Vincent Guittot , Ben Segall , Mel Gorman , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] sched/rt: cpupri_find: implement fallback mechanism for !fit case Message-ID: <20200218172745.hd7fxjqnzqkhfqx3@e107158-lin.cambridge.arm.com> References: <20200214163949.27850-1-qais.yousef@arm.com> <20200214163949.27850-2-qais.yousef@arm.com> <20200217234549.rpv3ns7bd7l6twqu@e107158-lin> <20200218114658.74236b3c@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200218114658.74236b3c@gandalf.local.home> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/18/20 11:46, Steven Rostedt wrote: > On Mon, 17 Feb 2020 23:45:49 +0000 > Qais Yousef wrote: > > > --- a/kernel/sched/rt.c > > +++ b/kernel/sched/rt.c > > @@ -14,6 +14,8 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun); > > > > struct rt_bandwidth def_rt_bandwidth; > > > > +typedef bool (*fitness_fn_t)(struct task_struct *p, int cpu); > > + > > static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer) > > { > > struct rt_bandwidth *rt_b = > > @@ -1708,6 +1710,7 @@ static int find_lowest_rq(struct task_struct *task) > > struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask); > > int this_cpu = smp_processor_id(); > > int cpu = task_cpu(task); > > + fitness_fn_t fitness_fn; > > > > /* Make sure the mask is initialized first */ > > if (unlikely(!lowest_mask)) > > @@ -1716,8 +1719,17 @@ static int find_lowest_rq(struct task_struct *task) > > if (task->nr_cpus_allowed == 1) > > return -1; /* No other targets possible */ > > > > + /* > > + * Help cpupri_find avoid the cost of looking for a fitting CPU when > > + * not really needed. > > + */ > > + if (static_branch_unlikely(&sched_asym_cpucapacity)) > > + fitness_fn = rt_task_fits_capacity; > > + else > > + fitness_fn = NULL; > > + > > if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask, > > - rt_task_fits_capacity)) > > + fitness_fn)) > > return -1; /* No targets found */ > > > > /* > > > If we are going to use static branches, then lets just remove the > parameter totally. That is, make two functions (with helpers), where > one needs this fitness function the other does not. > > if (static_branch_unlikely(&sched_asym_cpu_capacity)) > ret = cpupri_find_fitness(...); > else > ret = cpupri_find(...); > > if (!ret) > return -1; > > Something like that? Is there any implication on code generation here? I like my flavour better tbh. But I don't mind refactoring the function out if it does make it more readable. Thanks -- Qais Yousef