[openstack-dev] [nova] proposing feature for Liberty, would this need a spec?

Michael Still mikal at stillhq.com
Mon Mar 23 21:51:59 UTC 2015


I'm not 100% sure if this would be trivial or not, but the process to
find out isn't scary. We should add this to a nova meeting agenda on
the wiki and talk through it during a meeting.

(Noting that we're not approving specs for liberty in any form until
the Kilo branch is cut, so we have some time before we need to have
this discussion).

Michael

On Tue, Mar 24, 2015 at 7:58 AM, Chris Friesen
<chris.friesen at windriver.com> wrote:
> Hi,
>
> I'd like to propose (and implement) a feature for Liberty that would allow
> configuration of the pinning of the emulator when CPU pinning is enabled.
> (Currently the emulator is affined to the logical OR of all pCPUs used by
> the instance.)
>
> The general idea is to add an optional flavor extra spec (or image
> metadata):
>
> "hw:emulatorpin=<vcpulist>"
>
> If specified, this would affine the emulator to the pCPUs corresponding to
> the specified vCPUs.  If not specified, the emulator would be affined as it
> is currently.
>
> The rationale for this is that for pure userspace tasks we may want to give
> certain vCPUs as much CPU time as possible.  If the emulator is allowed to
> run run on the corresponding pCPU, then that robs the vCPU of some
> time--reducing throughput and increasing latency.
>
> Would something like this be eligible for the "trivial blueprint" process?
>
> Thanks,
> Chris
>
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