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

[Juergen Gross <juergen.gross@fujitsu-siemens.com>]

Jan Beulich wrote:
>>>> Juergen Gross <juergen.gross@fujitsu-siemens.com> 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

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