[dpdk-dev] [PATCH v4 00/10] VM Power Management

Paolo Bonzini pbonzini at redhat.com
Tue Dec 9 18:35:05 CET 2014


I had replied to this message, but my reply never got to the list.
Let's try again.

I wonder if this might be papering over a bug in the host cpufreq
driver.  If the guest is not doing much and leaving a lot of idle CPU
time, the host should scale down the frequency of that CPU.  In the case
of pinned VCPUs this should really "just work".  What is the problem
that is being solved?

Paolo

On 22/11/2014 18:17, Vincent JARDIN wrote:
> Tim,
> 
> cc-ing Paolo and qemu-devel@ again in order to get their take on it.
> 
>>>> Did you make any progress in Qemu/KVM community?
>>>> We need to be sync'ed up with them to be sure we share the same goal.
>>>> I want also to avoid using a solution which doesn't fit with their
>>>> plan.
>>>> Remember that we already had this problem with ivshmem which was
>>>> planned to be dropped.
>>>>
> 
>>> Unfortunately, I have not yet received any feedback:
>>> http://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg01103.html
>>
>> Just to add to what Alan said above, this capability does not exist in
>> qemu at the moment, and based on there having been no feedback on the
>> qemu mailing list so far, I think it's reasonable to assume that it
>> will not be implemented in the immediate future. The VM Power
>> Management feature has also been designed to allow easy migration to a
>> qemu-based solution when this is supported in future. Therefore, I'd
>> be in favour of accepting this feature into DPDK now.
>>
>> It's true that the implementation is a work-around, but there have
>> been similar cases in DPDK in the past. One recent example that comes
>> to mind is userspace vhost. The original implementation could also be
>> considered a work-around, but it met the needs of many in the
>> community. Now, with support for vhost-user in qemu 2.1, that
>> implementation is being improved. I'd see VM Power Management
>> following a similar path when this capability is supported in qemu.
> 
> Best regards,
>   Vincent
> 


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