Messages in this thread | | | Date | Tue, 04 Nov 2014 09:20:56 +0000 | From | Juri Lelli <> | Subject | Re: [PATCH RFC] sched/deadline: support dl task migrate during cpu hotplug |
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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
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