From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752523AbaKDJUx (ORCPT ); Tue, 4 Nov 2014 04:20:53 -0500 Received: from service87.mimecast.com ([91.220.42.44]:49148 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752459AbaKDJUs convert rfc822-to-8bit (ORCPT ); Tue, 4 Nov 2014 04:20:48 -0500 Message-ID: <54589A78.1060406@arm.com> Date: Tue, 04 Nov 2014 09:20:56 +0000 From: Juri Lelli User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Wanpeng Li , Peter Zijlstra CC: Ingo Molnar , Kirill Tkhai , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH RFC] sched/deadline: support dl task migrate during cpu hotplug References: <1414740497-7232-1-git-send-email-wanpeng.li@linux.intel.com> <20141103104111.GA23531@worktop.programming.kicks-ass.net> <20141103235747.GA26702@kernel> <20141104083225.GG10501@worktop.programming.kicks-ass.net> <20141104082345.GA22062@kernel> In-Reply-To: <20141104082345.GA22062@kernel> X-OriginalArrivalTime: 04 Nov 2014 09:20:44.0181 (UTC) FILETIME=[9C429C50:01CFF810] X-MC-Unique: 114110409204600701 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 04/11/14 08:23, Wanpeng Li wrote: > Hi Peter, > On Tue, Nov 04, 2014 at 09:32:25AM +0100, Peter Zijlstra wrote: >> On Tue, Nov 04, 2014 at 07:57:48AM +0800, Wanpeng Li wrote: >>> On Mon, Nov 03, 2014 at 11:41:11AM +0100, Peter Zijlstra wrote: >> >>>> On Fri, Oct 31, 2014 at 03:28:17PM +0800, Wanpeng Li wrote: >>>> So what is wrong with making dl_task_timer() deal with it? The timer >>>> will still fire on the correct time, canceling it and or otherwise >>>> messing with the CBS is wrong. Once it fires, all we need to do is >>>> migrate it to another cpu (preferably one that is still online of course >>>> :-). >> >>> Do you mean what I need to do is push the task to another cpu in dl_task_timer() >>> if rq is offline? >> >> That does indeed appear to be the sensible fix to me. >> >>> In addition, what will happen if dl task can't preempt on >>> another cpu? >> >> So if we find that the rq the task was on is no longer available, we >> need to select a new rq, the 'right' rq would be the one running the >> latest deadline. >> >> If it cannot preempt the latest (running) deadline, it was not eligible >> for running in the first place so no worries, right? > > I think this will lead to this deadline task cannot running on any rqs any more. > If my understanding is not right, when it will be picked? > I think you can just pick one random rq and move the task there. The push/pull mechanism should then move it around properly. Thanks, - Juri