linux-kernel - Re: [RFC PATCH v2] sched/deadline: support dl task migration during cpu hotplug

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Message-ID: <20141105105058.GQ3337@twins.programming.kicks-ass.net>
Date:	Wed, 5 Nov 2014 11:50:58 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@....com>,
	Kirill Tkhai <ktkhai@...allels.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] sched/deadline: support dl task migration during
 cpu hotplug

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.

Is this what you were asking?
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