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Re: [PATCH v2 2/2] credit: Don't steal vcpus which have yielded
- To: George Dunlap <george.dunlap@xxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Fri, 22 Sep 2023 01:30:36 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>
- Delivery-date: Fri, 22 Sep 2023 01:30:53 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v2 2/2] credit: Don't steal vcpus which have yielded
Hi George,
> On Sep 21, 2023, at 20:23, George Dunlap <george.dunlap@xxxxxxxxx> wrote:
>
> On large systems with many vcpus yielding due to spinlock priority
> inversion, it's not uncommon for a vcpu to yield its timeslice, only
> to be immediately stolen by another pcpu looking for higher-priority
> work.
>
> To prevent this:
>
> * Keep the YIELD flag until a vcpu is removed from a runqueue
>
> * When looking for work to steal, skip vcpus which have yielded
>
> NB that this does mean that sometimes a VM is inserted into an empty
> runqueue; handle that case.
>
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxx>
Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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