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Re: [pcp] Dynamic Proc PMDA metrics

To: Martins Innus <minnus@xxxxxxxxxxx>
Subject: Re: [pcp] Dynamic Proc PMDA metrics
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Wed, 12 Nov 2014 00:34:15 -0500 (EST)
Cc: pcp <pcp@xxxxxxxxxxx>
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <54627B7D.6040906@xxxxxxxxxxx>
References: <545D2CFA.1050600@xxxxxxxxxxx> <1477043892.10880496.1415600819766.JavaMail.zimbra@xxxxxxxxxx> <54627B7D.6040906@xxxxxxxxxxx>
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Thread-index: 0bTZEQfg56ZAVSYkJWorIr8i3STCkQ==
Thread-topic: Dynamic Proc PMDA metrics
Hi Martins,

----- Original Message -----
> [...]
> You can ignore all of this until I am done. I just wanted to get this
> out there since I don't know where in your cgroup work you are.  I think
> the only conflict might be in proc_pid.c with my addition of an extra
> parameter into some of the existing methods as I mentioned before.

Ah - OK - thanks for getting it out.  cgroups is progressing nicely, I'm
hoping end-of-this-week-ish it should be all revised.  So far, the rework
and refactoring is proving a neat improvement.

> 
> One thing I noticed and am trying to track down:
> 
> In the:
> 
> static void
> refresh_metrictable(pmdaMetric *source, pmdaMetric *dest, int id)
> 
> callback that I provide.  The domain doesn't appear to be set in the
> "source" at the time this call is made.  I check, and it is "0". But
> everything seems to work.  I assume this gets set at some later time?

Yeah, hmm, can't remember exactly how this works - but the domain number
usually gets stamped into the static metrictable at pmdaInit time.  ISTR
some need to pass the domain number around, in order to stamp it into
the dynamic metric PMIDs as well ... but its a vague memory.  This may be
an area where the dynamic metrics libpcp_pmda code could be improved too,
BTW - not sure, but keep that in mind (might be easier to pull the domain
number out of the pmdaExt structure and writing it into the source, if it
is missing at the time the callback is called?  I don't think that could
harm any existing PMDA code)

cheers.

--
Nathan

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