Date: Wed, 5 Nov 2014 13:52:54 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Wanpeng Li <wanpeng.li@linux.intel.com>, Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@arm.com>, Kirill Tkhai <ktkhai@parallels.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2] sched/deadline: support dl task migration during
 cpu hotplug
Message-ID: <20141105125254.GT3337@twins.programming.kicks-ass.net>
References: <1415177517-7189-1-git-send-email-wanpeng.li@linux.intel.com>
 <20141105105058.GQ3337@twins.programming.kicks-ass.net>
 <545A0317.4090406@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <545A0317.4090406@gmail.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org

On Wed, Nov 05, 2014 at 06:59:35PM +0800, Wanpeng Li wrote:
> Hi Peter,
> On 14/11/5 下午6:50, Peter Zijlstra wrote:
> >On Wed, Nov 05, 2014 at 04:51:57PM +0800, Wanpeng Li wrote:
> >>Note: dl task can be migrated successfully if rq is offline currently, however,
> >>I'm still not sure why task_rq(task)->rd->span just include the cpu which the dl
> >>task previous running on, so cpu_active_mask is used in the patch.
> >>
> >>Peterz, Juri?
> >So the root domain span is for exclusive cpusets
> >(Documentation/cgroups/cpusets.txt) where we fully separate sets of CPUs
> >and have no load-balancing between the sets.
> >
> >For 'normal' setups the rd->span is the entire machine, but using
> >cpusets you can create more (smaller) domains.
> 
> I don't setup any cpusets related stuff, however, task_rq(task)->rd->span
> just include the cpu which the dl task previous running on instead of the
> entire machine in find_later_rq().

Ah, it could be that for offline cpus we have a singleton rd. Lemme try
and remember wth we did there.
--
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/