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[Xen-devel] Re: CPU scheduling of domains and vcpus

To: "Mike D. Day" <ncmike@xxxxxxxxxx>
Subject: [Xen-devel] Re: CPU scheduling of domains and vcpus
From: Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>
Date: Mon, 21 Apr 2008 22:34:13 +0100
Cc: Nauman Rafique <naumanr@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Mike D. Day, le Mon 21 Apr 2008 16:32:18 -0400, a écrit :
> On 21/04/08 18:56 +0100, Samuel Thibault wrote:
> > Nauman Rafique, le Mon 21 Apr 2008 13:52:21 -0400, a écrit :
> > > In fact, wasted cycles can probably be avoided by doing opportunisitic
> > > gang scheduling (i.e. gang schedule, unless there would be wasted
> > > cycles)
> > 
> > How do you detect that there would be wasted cycles?
> The only way is for a very self-aware guest to use a paravirtual
> feature to give a hint to the scheduler. 

Agreed :)

> Alternatively, the scheduler can notify the guest that it is about to
> be preempted by the hypervisor and now would be a good time to sleep
> before gaining a contended spinlock.

Mmm, "about to be" means "on the next tick" then.  That may be a long


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