Re: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 02/09/2009 00:26, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:

> On 09/01/09 15:41, Dan Magenheimer wrote:
>> Won't pvclock+vsyscall have the same race?
> 
> Yes, it would need to be resolved either way.

The problem is a bit easier with vsyscall potentially. For example, give
each thread its own vsyscall clock data area (easy?), updated by kernel
whenever the thread is scheduled, and increment a version counter, checked
before and after by the vsyscall operation.

Well, I don't know how easy or fast that could actually be implemented, but
I'm at least confident it could work. But it does need kernel assistance.

 -- Keir



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