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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 19:41:39 +0100
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Nils Nieuwejaar <nils.nieuwejaar@xxxxxxxxx>, Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>, "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
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On Mon, Aug 11, 2008 at 03:50:57PM +0100, Keir Fraser wrote:

> >> What guarantee are you providing? Per thread, per address space, or global
> >> monotonicity?
> > 
> > Per thread non-strict monotonicity.
> Doesn't this just require thread-local storage and no lock?

The above is what we guarantee but it's not how it's implemented. All of
that is based upon the per-CPU hrtime, so we need the lock (or a
wholesale rework of how hrtime is managed in the Solaris kernel: that's
not going to happen :)


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