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Re: [libvirt] [PATCH 13/17] limit cpu bandwidth only for vcpus

On 08/03/2012 12:36 AM, Hu Tao wrote:
> This patch changes the behaviour of xml element cputune.period
> and cputune.quota to limit cpu bandwidth only for vcpus, and no
> longer limit cpu bandwidth for the whole guest.
> The reasons to do this are:
>   - This matches docs of cputune.period and cputune.quota.
>   - The other parts excepting vcpus are treated as "hypervisor",
>     and there are seperate period/quota settings for hypervisor

s/hypervisor/emulator/ throughout,

Is it worth being able to put a separate quota on the entire domain
(emulator+vcpus), independently from the smaller quotas on a per-vcpu or
per-emulator basis?  While I do think this is an appropriate fix
(normally, what we are trying to rate limit is the guest itself, and
that means run the emulator as fast as possible to let the guest keep
up), I do worry that it means someone that was previously using this to
limit the entire domain would now be oversubscribed, unless we also have
a way to preserve the ability to limit the entire domain.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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