Re: [PATCH 0/2][KVM] guest time accounting

Avi Kivity
2007-08-13T14:30:22Z

Laurent Vivier wrote:
> Christian Borntraeger wrote:
>
>> Am Freitag, 10. August 2007 schrieb Laurent Vivier:
>>
>>> The aim of these two patches is to measure the CPU time used by a virtual
>>> machine. All comments are welcome... I'm not sure it's the good way to do
>>>
>> that.
>>
>> I did something similar for or s390guest prototype, that Carsten posted in
>> May. I decided to account guest time to the user process instead of adding a
>> new field to avoid hazzle with old top. As you can read in the patch comment,
>> I personally prefer a new field if we can get one.
>>
>> My implementation uses a similar mechanism like hard and softirq. So I have an
>> sie_enter an sie_exit and a task_is_in_sie function - like irq_enter and
>> irq_exit. The main difference is based on the fact, that s390 has precise
>> accouting for irq, steal, user and system time, and therefore my patch is
>> based on architecture specifc code using CONFIG_VIRT_CPU_ACCOUNT.
>>
>> In general my patch has the same idea as your patch, so I am going to review
>> your patch and see if it would fit for s390.
>>
>> For reference this is the (never posted) old patch for our virtualisation
>> prototype. It wont work with kvm but it gives you the idea what we had in
>> mind on s390.
>>
>>
>
> thank you for your comment.
>
> As virtualization becomes very popular, perhaps we should implement something
> which could be used by all linux supported architectures ?
> (yes, I know it's non-sense for archs like m68k...)
> But my [PATCH 1/2] can be a good start (adding "guest" in cpustat)
> As guest accounting is hw dependent, I think we should add a hook in the
> accounting functions.
>

Isn't PF_VM exactly such a hook? All the hypervisor needs to do is to
set/unset it correctly?

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