Re: [BUG] Linux process vruntime accounting in Xen

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Wed, 2016-05-18 at 14:24 +0200, Juergen Gross wrote:
> On 17/05/16 11:33, George Dunlap wrote:
> > > Looks like CONFIG_PARAVIRT_TIME_ACCOUNTING is used for adjusting
> > > process
> > > times. KVM uses it but Xen doesn't.
> > Is someone on the Linux side going to put this on their to-do list
> > then? :-)
>
> Patch sent.
> 
Yep, seen it, thanks.

> Support was already existing for arm. 
>
Yes!! I remember Stefano talking about introducing it, and that was
also why I thought we had it already since long time on x86.

Well, anyway... :-)

> What is missing is support for
> paravirt_steal_rq_enabled which requires to be able to read the
> stolen
> time of another cpu. This can't work today as accessing another cpu's
> vcpu_runstate_info isn't possible without risking inconsistent data.
> I plan to add support for this, too, but this will require adding
> another hypercall to map a modified vcpu_runstate_info containing an
> indicator for an ongoing update of the data.
> 
Understood.

So, Tony, up for trying again your workload with this patch applied to
Linux?

Most likely, it _won't_ fix all the problems you're seeing, but I'm
curious to see if it helps.

Thanks again and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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