Re: Poor performance on HVM (kernbench)

[Steve Ofsthun <sofsthun@virtualiron.com>]

Todd Deshane wrote:
> On Wed, Sep 10, 2008 at 5:37 PM, Daniel Magenheimer
> <dan.magenheimer@oracle.com> 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 think what Dan is getting at is, the native execution run should restrict it's cpu and memory usage to be identical with the guest tests.  So restrict the native test cpus with "maxcpus=1" or "nosmp" on the boot line.  Similarly you can restrict memory using "mem=xxxM".

> 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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