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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 56461C43142 for ; Thu, 21 Jun 2018 19:04:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1293321A73 for ; Thu, 21 Jun 2018 19:04:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1293321A73 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org 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 S1754240AbeFUTE5 (ORCPT ); Thu, 21 Jun 2018 15:04:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:49150 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752650AbeFUTEz (ORCPT ); Thu, 21 Jun 2018 15:04:55 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 77EE821A6F; Thu, 21 Jun 2018 19:04:54 +0000 (UTC) Date: Thu, 21 Jun 2018 15:04:52 -0400 From: Steven Rostedt To: Byungchul Park 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: <20180621150452.4480c33f@gandalf.local.home> In-Reply-To: <1529297905-24703-2-git-send-email-byungchul.park@lge.com> References: <1529297905-24703-1-git-send-email-byungchul.park@lge.com> <1529297905-24703-2-git-send-email-byungchul.park@lge.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > (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; > } >