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

[Peter Zijlstra]

On Wed, Nov 05, 2014 at 06:59:35PM +0800, Wanpeng Li wrote:
> Hi Peter,
> On 14/11/5 äå6:50, 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.
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