Re: [Xen-devel] [BUG] Linux process vruntime accounting in Xen

[Juergen Gross <jgross@xxxxxxxx>]

On 18/05/16 18:14, Juergen Gross wrote:
> On 18/05/16 18:09, Tony S wrote:
>> On Wed, May 18, 2016 at 8:57 AM, Dario Faggioli
>> <dario.faggioli@xxxxxxxxxx> wrote:
>>> 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.
>>
>> Hi Dario,
>>
>> I did not see the patch. Can you please send me the patch and I will
>> try to test it later.
> 
> Here is an updated version.

Tony, would you be interested to test a complete solution?

This would require to use a Xen 4.7 hypervisor with some patches applied
and some patches for the Linux kernel (I've done some basic tests with
kernel 4.6). I've attached the patches in case you want to try them. :-)
You should set CONFIG_PARAVIRT_TIME_ACCOUNTING=y in the kernel .config


Juergen

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