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Re: [Xen-devel] Re: [PATCH] [RFC] Credit2 scheduler prototype

To: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH] [RFC] Credit2 scheduler prototype
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 08 Dec 2009 18:20:53 +0000
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On 08/12/2009 14:48, "George Dunlap" <George.Dunlap@xxxxxxxxxxxxx> wrote:

> My main concern is that sharing the runqueue between cores requires
> some changes to the core context switch code. The kinks aren't 100%
> worked out yet, so there's a risk that there will be an impact on the
> correctness of the credit1 scheduler.

Ah, if that's the problem with selecting a vcpu which happens to still be
'is_running' then I had some ideas how you could deal with that within the
credit2 scheduler. If you see such a vcpu when searching the runqueue,
ignore it, but set VPF_migrating. You'll then get a 'pick_cpu' callback when
descheduling of the vcpu is completed. That should play nice with the lazy
context switch logic while keeping things work conserving.

 -- Keir

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