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Re: [Xen-devel] Linux spin lock enhancement on xen

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Subject: Re: [Xen-devel] Linux spin lock enhancement on xen
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 18 Aug 2010 18:09:22 +0100
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On 18/08/2010 17:37, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:

> I don't see why the guest should micromanage Xen's scheduler decisions.
> If a VCPU is waiting for another VCPU and can put itself to sleep in the
> meantime, then its up to Xen to take advantage of that newly freed PCPU
> to schedule something.  It may decide to run something in your domain
> that's runnable, or it may decide to run something else.  There's no
> reason why the spinlock holder is the best VCPU to run overall, or even
> the best VCPU in your domain.
> My view is you should just put any VCPU which has nothing to do to
> sleep, and let Xen sort out the scheduling of the remainder.

Yeah, I'm no fan of yield or yield-to type operations. I'd reserve the right
to implement both of them as no-op.

 -- Keir

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