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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 E2C10C48BE7 for ; Mon, 8 Jul 2019 08:41:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B476B2064B for ; Mon, 8 Jul 2019 08:41:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729301AbfGHIls (ORCPT ); Mon, 8 Jul 2019 04:41:48 -0400 Received: from mail.santannapisa.it ([193.205.80.98]:30743 "EHLO mail.santannapisa.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727976AbfGHIls (ORCPT ); Mon, 8 Jul 2019 04:41:48 -0400 X-Greylist: delayed 3600 seconds by postgrey-1.27 at vger.kernel.org; Mon, 08 Jul 2019 04:41:46 EDT Received: from [151.41.66.174] (account l.abeni@santannapisa.it HELO sweethome) by santannapisa.it (CommuniGate Pro SMTP 6.1.11) with ESMTPSA id 140626216; Mon, 08 Jul 2019 09:41:44 +0200 Date: Mon, 8 Jul 2019 09:41:36 +0200 From: luca abeni To: Dietmar Eggemann Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , "Rafael J . Wysocki" , Ingo Molnar , Peter Zijlstra , Vincent Guittot , "Paul E . McKenney" , Joel Fernandes , Quentin Perret , Luc Van Oostenryck , Morten Rasmussen , Juri Lelli , Daniel Bristot de Oliveira , Patrick Bellasi , Tommaso Cucinotta Subject: Re: [RFC PATCH 2/6] sched/dl: Capacity-aware migrations Message-ID: <20190708094136.7bce5f46@sweethome> In-Reply-To: References: <20190506044836.2914-1-luca.abeni@santannapisa.it> <20190506044836.2914-3-luca.abeni@santannapisa.it> X-Mailer: Claws Mail 3.17.3 (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 Hi Dietmar, On Thu, 4 Jul 2019 14:05:22 +0200 Dietmar Eggemann wrote: > On 5/6/19 6:48 AM, Luca Abeni wrote: > > [...] > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > index 5b981eeeb944..3436f3d8fa8f 100644 > > --- a/kernel/sched/deadline.c > > +++ b/kernel/sched/deadline.c > > @@ -1584,6 +1584,9 @@ select_task_rq_dl(struct task_struct *p, int > > cpu, int sd_flag, int flags) if (sd_flag != SD_BALANCE_WAKE) > > goto out; > > > > + if (dl_entity_is_special(&p->dl)) > > + goto out; > > I wonder if this is really required. The if condition > > 1591 if (unlikely(dl_task(curr)) && > 1592 (curr->nr_cpus_allowed < 2 || > 1593 !dl_entity_preempt(&p->dl, &curr->dl)) && > 1594 (p->nr_cpus_allowed > 1)) { > > further below uses '!dl_entity_preempt(&p->dl, &curr->dl))' which > returns 'dl_entity_is_special(a) || ...' Uhm... I do not remember the details; I remember that the check fixed something during the development of the patchset, but I did not check if it was still needed when I forward-ported the patches... So, maybe it worked around some bugs in previous versions of the kernel, but is not needed now. Luca