openstack team mailing list archive

[Doug Hellmann <doug.hellmann@xxxxxxxxxxxxx>]

On Wed, Oct 31, 2012 at 11:25 AM, Eoghan Glynn <eglynn@xxxxxxxxxx> wrote:

>
>
> > > I don't think (max - min) would suffice to give an accurate
> > > measure of the actual CPU time used, as the counter may have
> > > reset multiple times in the course of the requested duration.
> >
> > It is, because /max in the API should be aware of the fact a
> > reset can occur and computes accordingly. We started to discuss
> > this a bit in:
> >
> >       https://bugs.launchpad.net/ceilometer/+bug/1061817
>
> A-ha, OK, so not so much (max - min) as:
>
>    (\Sigma local maxima) - first
>
> Sounds computationally expensive to produce on the fly, but maybe
> the local maxima can be efficiently recorded as the data is being
> ingested.
>

Is that better than just reporting the data in a more easily digested
format in the first place?

Julien, I don't understand your comment about losing data "if your system
is not launched to compute delta". Can you clarify what you mean there? I
do understand that the agent would need to store state about the counter
locally in order to track the delta value, but I think we could provide a
convenient way for pollsters to do that without complicating them
excessively.

Doug



>
> Cheers,
> Eoghan
>
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