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Re: [Xen-devel] [Patch 2 of 2]: PV-domain SMP performance Linux-part

  • To: Jan Beulich <jbeulich@xxxxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>
  • Date: Fri, 19 Dec 2008 11:48:20 +0100
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Delivery-date: Fri, 19 Dec 2008 02:49:25 -0800
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Jan Beulich wrote:
>>>> Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx> 19.12.08 11:06 >>>
>> Regarding handling this in Xen only: not to deschedule a vcpu in case of
>> interrupts disabled is easy, but how would you deschedule it after interrupts
>> are allowed again?
> It's all the same as with the newly added flag of yours - it requires 
> cooperation
> from the guest (plus the forced de-schedule if it fails to do so). It's just 
> that
> you don't need to set two flags when disabling interrupts, that second flag
> would only be needed when you want to avoid being de-scheduled for
> reasons other than event delivery being disabled.

Just another thought:
My approach was more compatible. Only a guest which is aware of the new flag
will set it and in turn respect the request of the hypervisor to give up
control after enabling de-scheduling again.
Old guests would always be regarded as non-cooperative.


Juergen Gross                             Principal Developer
IP SW OS6                      Telephone: +49 (0) 89 636 47950
Fujitsu Siemens Computers         e-mail: juergen.gross@xxxxxxxxxxxxxxxxxxx
Otto-Hahn-Ring 6                Internet: www.fujitsu-siemens.com
D-81739 Muenchen         Company details: www.fujitsu-siemens.com/imprint.html

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