[libvirt] CFS Hardlimits and the libvirt cgroups implementation

[Adam Litke]

On 06/10/2011 04:45 AM, Wen Congyang wrote:
>>> === 3 ===
>>> Besides the above issues, I would like to open a discussion on what the
>>> libvirt API for enabling cpu hardlimits should look like.  Here is what
>>> I was thinking:
>>>
>>> Two additional scheduler parameters (based on the names given in the
>>> cgroup fs) will be recognized for qemu domains: 'cfs_period' and
>>> 'cfs_quota'.  These can use the existing
>>> virDomain[Get|Set]SchedulerParameters() API.  The Domain XML schema
>>> would be updated to permit the following:
>>>
>>> --- snip ---
>>> <cputune>
>>>   ...
>>>   <cfs_period>1000000</cfs_period>
>>>   <cfs_quota>500000</cfs_quota>
>>> </cputune>
>>> --- snip ---
>>
>> I don't think 'cfs_' should be in the names here. These absolute
>> limits on CPU time could easily be applicable to non-CFS schedulars
>> or non-Linux hypervisors.
> 
> Do you mean the element's name should be period and quota?
> 
> The name of the file provided by cfs bandwidth is:cpu.cfs_period_us
> and cpu.cfs_quota_us.
> 
> I think he uses 'cfs_' because it's similar as the filename.
> But I do not mind the element's name.
> 
> I am making the patch, so I want to know which element's name should
> be used.

I think it's a good idea to use 'period' and 'quota'.  In my other email
I suggest that the unit for period should be microseconds and quota
should be a percentage of the period.  That way quota can be used
without needing to know or change the default period.

Please Cc: me on your patch.  We are very interested in this feature and
would like to review/test it.

-- 
Adam Litke
IBM Linux Technology Center