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

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

Keir,

What do you think of the attached patches?

The first implements something like what you suggest below, but
instead of using a sort of "hack" with VPF_migrate, it makes a proper
"context_saved" SCHED_OP callback.

The second addresses the fact that when sharing runqueues,
v->processor may change quickly without an explicit migrate.

The last two are the credit2 hypervisor and tool patches, which use
these two changes (for reference).

I think these patches should be basically NOOP for the existing
schedulers, so as far as I'm concerned they're ready to be merged as
soon as you're happy with them.

Peace,
 -George

On Tue, Dec 8, 2009 at 6:20 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
> 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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Attachment: context_switch-vcpu-processor-sync.diff
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Attachment: credit2-hypervisor.diff
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Attachment: credit2-tools.diff
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