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    SubjectRe: [RFC] CPU hard limits
    On Thu, Jun 04, 2009 at 03:19:22PM +0300, Avi Kivity wrote:
    > Bharata B Rao wrote:
    >> 2. Need for hard limiting CPU resource
    >> --------------------------------------
    >> - Pay-per-use: In enterprise systems that cater to multiple clients/customers
    >> where a customer demands a certain share of CPU resources and pays only
    >> that, CPU hard limits will be useful to hard limit the customer's job
    >> to consume only the specified amount of CPU resource.
    >> - In container based virtualization environments running multiple containers,
    >> hard limits will be useful to ensure a container doesn't exceed its
    >> CPU entitlement.
    >> - Hard limits can be used to provide guarantees.
    > How can hard limits provide guarantees?
    > Let's take an example where I have 1 group that I wish to guarantee a
    > 20% share of the cpu, and anther 8 groups with no limits or guarantees.
    > One way to achieve the guarantee is to hard limit each of the 8 other
    > groups to 10%; the sum total of the limits is 80%, leaving 20% for the
    > guarantee group. The downside is the arbitrary limit imposed on the
    > other groups.

    This method sounds very similar to the openvz method:

    > 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 ?


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