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Re: [PATCH-for-4.17 v3] xen/sched: migrate timers to correct cpus after suspend


  • To: Juergen Gross <jgross@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Dario Faggioli <dfaggioli@xxxxxxxx>
  • Date: Fri, 4 Nov 2022 07:48:47 +0000
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  • Cc: "Henry.Wang@xxxxxxx" <Henry.Wang@xxxxxxx>, "marmarek@xxxxxxxxxxxxxxxxxxxxxx" <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, "george.dunlap@xxxxxxxxxx" <george.dunlap@xxxxxxxxxx>, "mengxu@xxxxxxxxxxxxx" <mengxu@xxxxxxxxxxxxx>
  • Delivery-date: Fri, 04 Nov 2022 07:48:52 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHY7svfW5RCRD6BzEauaEQnxR7xn64uZiOA
  • Thread-topic: [PATCH-for-4.17 v3] xen/sched: migrate timers to correct cpus after suspend

On Wed, 2022-11-02 at 16:00 +0100, Juergen Gross wrote:
> Today all timers are migrated to cpu 0 when the system is being
> suspended. They are not migrated back after resuming the system
> again.
> 
> This results (at least) to visible problems with the credit
> scheduler,
> as the timer isn't handled on the cpu it was expected to occur, which
> will result in an ASSERT() triggering. Other more subtle problems,
> like
> uninterrupted elongated time slices, are probable. The least effect
> will be worse performance on cpu 0 resulting from most scheduling
> related timer interrupts happening there after suspend/resume.
> 
> Add migrating the scheduling related timers of a specific cpu from
> cpu
> 0 back to its original cpu when that cpu has gone up when resuming
> the
> system.
> 
> Fixes: 0763cd268789 ("xen/sched: don't disable scheduler on cpus
> during suspend")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Tested-by: Marek Marczykowski-Górecki
> <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
>
Acked-by: Dario Faggioli <dfaggioli@xxxxxxxx>

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

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