Re: [Xen-devel] Xen Performance Results

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Hi George,

Thank you for your reply.

On 12/22/2017 11:26 AM, George Dunlap wrote:
> On Thu, Dec 21, 2017 at 2:42 PM, Sergej Proskurin
> <proskurin@xxxxxxxxxxxxx> wrote:
>> Hi all,
>>
>> For the sake of completeness: the solution to the issue stated in my
>> last email was deactivating Intel's Turbo Boost technology directly in
>> UEFI (deactivating Turbo Boost through xenpm was not enough). Apparently
>> Turbo Boost affects Linux and KVM differently than Xen, which led to the
>> phonomenon, in which the benchmark execution on Xen appeared faster than
>> on bare metal.
> 
> *Appeared* faster than on bare metal, or *was* faster than on bare metal?
> 
> If the source of the change was the Turbo Boost, it's entirely
> possible that the difference is due to the placement of workers on
> cpus -- i.e., that Linux's bare metal scheduler makes a worse choice
> for this particular workload than Xen's scheduler does.
> 

Given the fact that for this particular benchmark I configured both dom0
and domu to using only one core (in fact I have pinned both domains to
the same physical core), I do not believe that the performance increase
was due to a better placement on all available CPU's. However, I
absolutely agree that there might be a difference in handling Turbo
Boosts between Linux and Xen.

Thanks,
~Sergej

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