From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751249AbdKTNkO (ORCPT ); Mon, 20 Nov 2017 08:40:14 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:42893 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751109AbdKTNkL (ORCPT ); Mon, 20 Nov 2017 08:40:11 -0500 X-Google-Smtp-Source: AGs4zMb/Zf0/ZClTeAwHUPOdJ2/8OQDBCjir+46tsWo26zoaamqDqwHZTIzZzrctpJHsBgR+++eKFQ== Subject: Re: [PATCH v3 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value To: Byungchul Park , peterz@infradead.org, mingo@kernel.org, rostedt@goodmis.org Cc: tglx@linutronix.de, raistlin@linux.it, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, kernel-team@lge.com References: <1510616805-15380-1-git-send-email-byungchul.park@lge.com> <1510616805-15380-2-git-send-email-byungchul.park@lge.com> From: Daniel Bristot de Oliveira Message-ID: <45e1f4e5-685b-88cd-caca-8d22a81d13cb@redhat.com> Date: Mon, 20 Nov 2017 14:40:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1510616805-15380-2-git-send-email-byungchul.park@lge.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/14/2017 12:46 AM, Byungchul Park wrote: > Currently, migrating tasks to cpu0 unconditionally happens when the > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0). > We have to distinguish between the empty case and cpu0 to avoid the > unnecessary migrations. Therefore, it has to return an invalid value > e.i. -1 in that case. > > Signed-off-by: Byungchul Park > Acked-by: Steven Rostedt (VMware) Acked-by: Daniel Bristot de Oliveira Thanks! -- Daniel > --- > kernel/sched/cpudeadline.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > index 9f02035..bcf903f 100644 > --- a/kernel/sched/cpudeadline.c > +++ b/kernel/sched/cpudeadline.c > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > int best_cpu = cpudl_maximum_cpu(cp); > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > + /* > + * The heap tree is empty for now, just return. > + */ > + if (best_cpu == -1) > + return 0; > + > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) && > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) { > if (later_mask) > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp) > return -ENOMEM; > } > > - for_each_possible_cpu(i) > + for_each_possible_cpu(i) { > + cp->elements[i].cpu = -1; > cp->elements[i].idx = IDX_INVALID; > + } > > return 0; > } >