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Re: [Xen-devel] RE: [PATCH] rendezvous-based local time calibration WOW!

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] RE: [PATCH] rendezvous-based local time calibration WOW!
From: John Levon <levon@xxxxxxxxxxxxxxxxx>
Date: Mon, 11 Aug 2008 15:43:53 +0100
Cc: "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Nils Nieuwejaar <nils.nieuwejaar@xxxxxxxxx>, Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
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On Mon, Aug 11, 2008 at 03:38:31PM +0100, Keir Fraser wrote:

> > It's only non-zero if we can indeed reschedule fast enough. If it's now
> > below the threshold, then we can consider it effectively fixed. Only
> > testing can really tell us that.
> Depending on how critical this guarantee is, I wouldn't rely on Xen to
> perform perfectly. Probably you should keep your lock.

Or maybe make it optional, and let people turn it on when VCPUs are
pinned (VCPU migration doesn't make much sense to me for server
workloads AFAICS).

That lock is *painful*.


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