Re: [Xen-devel] Xen Benchmarking guidelines

[Keir Fraser <keir@xxxxxxxxxxxxx>]

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
guest.

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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