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

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Linux spin lock enhancement on xen
From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Date: Wed, 18 Aug 2010 19:52:31 -0700
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "Xen-devel@xxxxxxxxxxxxxxxxxxx" <Xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Wed, 18 Aug 2010 18:09:22 +0100
Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:

> 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

I think making them advisory makes sense. Ultimately xen decides. 


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