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RE: [Xen-devel] Poor performance on HVM (kernbench)

To: deshantm@xxxxxxxxx
Subject: RE: [Xen-devel] Poor performance on HVM (kernbench)
From: Daniel Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 10 Sep 2008 14:45:26 -0700 (PDT)
Cc: xen-devel mailing list <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Perhaps you should run the native with nosmp then, to ensure
the comparison isn't taken out of context.

> -----Original Message-----
> From: Todd Deshane [mailto:deshantm@xxxxxxxxx]
> Sent: Wednesday, September 10, 2008 3:42 PM
> To: Daniel Magenheimer
> Cc: xen-devel mailing list
> Subject: Re: [Xen-devel] Poor performance on HVM (kernbench)
> 
> 
> On Wed, Sep 10, 2008 at 5:37 PM, Daniel Magenheimer
> <dan.magenheimer@xxxxxxxxxx> wrote:
> > This doesn't answer the HVM question but it appears that
> > you are running guests with 1 vCPU but comparing against
> > a dual-CPU native.  True?
> 
> Yes. The intuition is that we don't want to overcommit virtual CPUs
> since then you are stressing the schedulers more.
> 
> I ran some tests with 2 vCPUs and all the numbers are a bit higher (as
> having two CPUs tackling a compile is faster).
> 
> Although overcommit (of CPUs and memory ;) is interesting, we leave a
> CPU dedicated to the host system (linux/dom0)
> on purpose.
> 
> Todd
> 
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