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_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 A9A52C43143 for ; Fri, 22 Jun 2018 02:13:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6040323C3F for ; Fri, 22 Jun 2018 02:13:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6040323C3F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lge.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934302AbeFVCNX (ORCPT ); Thu, 21 Jun 2018 22:13:23 -0400 Received: from lgeamrelo13.lge.com ([156.147.23.53]:54142 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933905AbeFVCNW (ORCPT ); Thu, 21 Jun 2018 22:13:22 -0400 Received: from unknown (HELO lgemrelse7q.lge.com) (156.147.1.151) by 156.147.23.53 with ESMTP; 22 Jun 2018 11:13:19 +0900 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: byungchul.park@lge.com Received: from unknown (HELO X58A-UD3R) (10.177.222.33) by 156.147.1.151 with ESMTP; 22 Jun 2018 11:13:19 +0900 X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Fri, 22 Jun 2018 11:13:16 +0900 From: Byungchul Park To: Steven Rostedt Cc: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, raistlin@linux.it, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, bristot@redhat.com, kernel-team@lge.com, joel@joelfernandes.org Subject: Re: [RESEND PATCH v5 2/2] sched/deadline: Set cp->elements[0].cpu to -1 when the heap is empty Message-ID: <20180622021316.GA17010@X58A-UD3R> References: <1529297905-24703-1-git-send-email-byungchul.park@lge.com> <1529297905-24703-2-git-send-email-byungchul.park@lge.com> <20180621150452.4480c33f@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180621150452.4480c33f@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 21, 2018 at 03:04:52PM -0400, Steven Rostedt wrote: > On Mon, 18 Jun 2018 13:58:25 +0900 > Byungchul Park wrote: > > > Hello Steven and Daniel, > > > > I've changed the 2nd patch a little bit to consider cpudl_clear() > > additionally. Can I keep your Acked-by on? > > Actually, I think this should be a separate patch. It handles a > different issue. Do you think this should be a separate patch even though both are anyway for considering empty one properly? OK, I will then. Thanks a lot, Steve. > > (I temporarily removed the Acked-by you gave me.) > > > > Acked-by: Steven Rostedt (VMware) > > Acked-by: Daniel Bristot de Oliveira > > > > -----8<----- > > >From 1e368d276186c22f9da298206c718b33e805828d Mon Sep 17 00:00:00 2001 > > From: Byungchul Park > > Date: Mon, 4 Jun 2018 15:05:08 +0900 > > Subject: [RESEND PATCH v5 2/2] sched/deadline: Set cp->elements[0].cpu to -1 when the > > heap is empty > > > > Currently, migrating tasks to cpu0 unconditionally happens when the > > heap is empty, since cp->elements[0].cpu is 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 the case the heap is empty. > > > > Signed-off-by: Byungchul Park > > Suggested-by: Joel Fernandes > > --- > > kernel/sched/cpudeadline.c | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > > index ae4fbdc..a200b36 100644 > > --- a/kernel/sched/cpudeadline.c > > +++ b/kernel/sched/cpudeadline.c > > @@ -136,6 +136,10 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > > > > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > > > + /* The heap tree is empty, just return. */ > > + if (best_cpu == -1) > > + return 0; > > + > > Actually, why not put the if before the WARN_ON, and then we can > simplify the WARN_ON: > > if (best_cpu == -1) > return 0; > > WARN_ON(!cpu_present(best_cpu)); > > -- Steve > > > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) && > > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) { > > if (later_mask) > > @@ -172,6 +176,13 @@ void cpudl_clear(struct cpudl *cp, int cpu) > > * This could happen if a rq_offline_dl is > > * called for a CPU without -dl tasks running. > > */ > > + } else if (cp->size == 1){ > > + /* Only one element in the heap, clear it. */ > > + cp->elements[0].cpu = -1; > > + cp->elements[cpu].idx = IDX_INVALID; > > + cp->size = 0; > > + > > + cpumask_set_cpu(cpu, cp->free_cpus); > > } else { > > new_cpu = cp->elements[cp->size - 1].cpu; > > cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl; > > @@ -267,6 +278,9 @@ int cpudl_init(struct cpudl *cp) > > for_each_possible_cpu(i) > > cp->elements[i].idx = IDX_INVALID; > > > > + /* Mark heap as initially empty. */ > > + cp->elements[0].cpu = -1; > > + > > return 0; > > } > >