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Re: [Xen-devel] Poor HVM performance with 8 vcpus

  • To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Wed, 14 Oct 2009 11:11:42 +0200
  • Cc: Gianluca Guida <Gianluca.Guida@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 14 Oct 2009 02:12:11 -0700
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Keir Fraser wrote:
> On 14/10/2009 09:16, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:
>> as the performance of BS2000 seems to be hit by OOS optimization, I'm
>> thinking of making a patch to disable this feature by a domain parameter.
>> Is there a way to do this without having to change all places where the
>> #if statements are placed?
>> I think there should be some central routines where adding an "if" could
>> be enough (setting oos_active to 0 seems not to be enough, I fear).
>> Do you have any hint?
> How about disabling it for domains with more than four VCPUs? Have you
> measured performance with OOS for 1-4 VCPU guests? This is perhaps not
> something that needs to be baked into guest configs.

The same benchmark with 4 vcpus showed an improvement of about 6 % with OOS
disabled. A 1 vcpu BS2000 showed no change in performance.

And as Tim writes: there are systems with more than 4 vcpus which are still
faster with OOS optimization active.


Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 636 47950
Fujitsu Technolgy Solutions               e-mail: juergen.gross@xxxxxxxxxxxxxx
Otto-Hahn-Ring 6                        Internet: ts.fujitsu.com
D-81739 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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