Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753731AbaKLXXP (ORCPT ); Wed, 12 Nov 2014 18:23:15 -0500 Received: from mga03.intel.com ([134.134.136.65]:22961 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752692AbaKLXXO (ORCPT ); Wed, 12 Nov 2014 18:23:14 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,691,1406617200"; d="scan'208";a="487028924" Date: Thu, 13 Nov 2014 07:02:17 +0800 From: Wanpeng Li To: Peter Zijlstra Cc: Juri Lelli , Wanpeng Li , Ingo Molnar , Kirill Tkhai , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v5] sched/deadline: support dl task migration during cpu hotplug Message-ID: <20141112230217.GB23249@kernel> Reply-To: Wanpeng Li References: <1415754413-13988-1-git-send-email-wanpeng.li@linux.intel.com> <546377FC.4090408@arm.com> <20141112153906.GL29390@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141112153906.GL29390@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On Wed, Nov 12, 2014 at 04:39:06PM +0100, Peter Zijlstra wrote: >On Wed, Nov 12, 2014 at 03:08:44PM +0000, Juri Lelli wrote: >> > @@ -1185,8 +1223,9 @@ static int find_later_rq(struct task_struct *task) >> > * We have to consider system topology and task affinity >> > * first, then we can look for a suitable cpu. >> > */ >> > - cpumask_copy(later_mask, task_rq(task)->rd->span); >> > - cpumask_and(later_mask, later_mask, cpu_active_mask); >> > + cpumask_copy(later_mask, cpu_active_mask); >> > + if (likely(task_rq(task)->online)) >> > + cpumask_and(later_mask, later_mask, task_rq(task)->rd->span); >> >> So, here you consider the span only when the task_rq is online, >> but there might be others cpus still online belonging to the same >> rd->span. And you have to consider them when migrating. Actually, >> migration must still be restricted to the online cpus of task's >> original rd->span, or I fear you can break clustered scheduling. > >Ah, good point that, we must somehow find the right root domain to >'restore' the task to. Now I'm not entirely sure we still have this. >Lemme ponder that. Any idea is a great appreciated. :-) Regards, Wanpeng Li -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/