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Re: [Xen-devel] Xen Benchmarking guidelines

To: "Nick L. Petroni Jr." <npetroni@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen Benchmarking guidelines
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Tue, 14 Aug 2007 11:53:36 +0100
Cc: Michael Hicks <mwh@xxxxxxxxxx>
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On 14/8/07 11:37, "Nick L. Petroni Jr." <npetroni@xxxxxxxxxx> wrote:

> In general, I'm using standard benchmarking best practices, i.e.,
> disabling unnecessary services in host and guest, etc. Perhaps this is
> related to VCPU scheduling? Should I try pinning a vcpu? Please let
> me know if I can provide more details. Any help or insight would be much
> appreciated!

It should be possible, and in fact difficult not, to get almost native
scores on SPECINT benchmarks from within an HVM guest. There's no I/O or
system activity at all -- it's just measuring raw CPU speed.

The most likely culprits are scheduling problems or time problems in the HVM

To discount scheduling issues, it's probably worth pinning your HVM VCPU to
a single physical CPU (and set the affinity of dom0 so that it *doesn't* run
on that physical CPU) and see if that helps.

For time issues, you can time your SPECINT runs with a stopwatch. Or perhaps
you can come with some more automatable means, but you should aim to take
before/after timestamps from *outside* the HVM guest, since you're trying to
ascertain whether the HVM timekeeping is screwed on your system.

 -- Keir

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