[Devel] Re: [RFC] CPU hard limits

[Balbir Singh]

On Fri, Jun 5, 2009 at 11:33 AM, Avi Kivity <avi at redhat.com> wrote:
> Bharata B Rao wrote:
>>>
>>> Another way is to place the 8 groups in a container group, and limit
>>>  that to 80%. But that doesn't work if I want to provide guarantees to
>>>  several groups.
>>>
>>
>> Hmm why not ? Reduce the guarantee of the container group and provide
>> the same to additional groups ?
>>
>
> This method produces suboptimal results:
>
> $ cgroup-limits 10 10 0
> [50.0, 50.0, 40.0]
>
> I want to provide two 10% guaranteed groups and one best-effort group.
>  Using the limits method, no group can now use more than 50% of the
> resources.  However, having the first group use 90% of the resources does
> not violate any guarantees, but it not allowed by the solution.
>

How, it works out fine in my calculation

50 + 40 for G2 and G3, make sure that G1 gets 10%, since others are
limited to 90%
50 + 40 for G1 and G3, make sure that G2 gets 10%, since others are
limited to 90%
50 + 50 for G1 and G2, make sure that G3 gets 0%, since others are
limited to 100%

Now if we really have zeros, I would recommend using

cgroup-limits 10 10 and you'll see that you'll get 90, 90 as output.

Adding zeros to the calcuation is not recommended. Does that help?

Balbir
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