openstack team mailing list archive

[Julien Danjou <julien@xxxxxxxxxxx>]

On Wed, Oct 31 2012, Eoghan Glynn wrote:

> Would that total usage be much more apparent if we started
> metering the delta between CPU times on subsequent polling
> periods as a gauge measure? (As opposed to treating it as
> a cumulative measure)

I'm rather against the idea of transforming all cumulative counters to
delta, for the simple reason that this imply to lose information if your
system is not launched to compute delta, or that you have to maintaint a
previous value accross restart.
The API will be capable to do the operation you need, no matter what the
type of counter is (delta or cumulative).

> 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

-- 
Julien Danjou
# Free Software hacker & freelance
# http://julien.danjou.info

Attachment: pgpYg2h0yP_K7.pgp
Description: PGP signature