[collectd] [PATCH] New plugin - lpar

[Florian Forster]

Hi Aurélien,

On Tue, Sep 07, 2010 at 11:50:09AM +0200, Aurélien Reynaud wrote:
> > Many people expect the CPU usage to be in percent. You can easily
> > calculate that in the front-end as

> What I am saying here is that we cannot just compute a ratio with the
> raw counters, we need to have the final result expressed in CPUs.

You're right: While it is of course possible to calculate the
percentages of one status to the sum of all status, it is much more
interesting to take the "entitlement" as reference. Since "uncapped"
partitions can use more ticks than they are entitled to, calculating a
percentage relative to the entitlement becomes impossible, leave alone
something relative to the entire processor pool.

> What I am saying here is that we cannot just compute a ratio with the
> raw counters, we need to have the final result expressed in CPUs.

Yeah, since the LPAR documentation itself always talks in terms of
"virtual CPUs" we might as well adopt that terminology in the plugin.

Currently I tend towards the solution I think you originally
implemented: Introduce a "vcpu_gauge" (or simply "vcpu") type and track
usage in terms of virtual CPUs. I.e. if the partition spends 123% of a
virtual CPU executing user code, store 1.23 in the "user" value.

Best regards,
--octo
-- 
Florian octo Forster
Hacker in training
GnuPG: 0x0C705A15
http://octo.it/
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