Re: [kvm-devel] [PATCH 0/4] Virtual Machine Time Accounting

Avi Kivity
2007-08-21T12:54:46Z

Jeremy Fitzhardinge wrote:
> Laurent Vivier wrote:
>
>> functionnalities:
>>
>> - allow to measure time spent by a CPU in a virtual CPU.
>> - allow to display in /proc/state this value by CPU
>> - allow to display in /proc/<pid>/state this value by process
>> - allow KVM to use these 3 previous functionnalities
>>
>>
>
> So, currently time spent in a kvm guest is accumulated as qemu-kvm
> usertime, right? Given that qemu knows when its running in qemu vs
> guest context, couldn't it provide the breakdown between user and guest
> time (ditto lguest)?
>

qemu doesn't (and shouldn't) do accounting; that's best done by
interrupt driven code.

The patches do account for guest time in a separate counter; guest time
is added to both user time and the new counter. This allows an old
'top' to see guest time (accounted as user time), and a new 'top' to
separate guest time and user time by performing the appropriate
mathematical operation.

--
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