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Re: [pcp] [RFC] Reducing installed PCP package sizes

To: Mark Goodwin <mgoodwin@xxxxxxxxxx>
Subject: Re: [pcp] [RFC] Reducing installed PCP package sizes
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Wed, 17 Sep 2014 19:26:38 -0400 (EDT)
Cc: PCP <pcp@xxxxxxxxxxx>
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <5418DC6E.7080304@xxxxxxxxxx>
References: <236430128.44517548.1409912159545.JavaMail.zimbra@xxxxxxxxxx> <5418DC6E.7080304@xxxxxxxxxx>
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Thread-index: VAHFP1N+AVgHf9THbH4jiZ2SvWcdYw==
Thread-topic: Reducing installed PCP package sizes
Hi Mark,

----- Original Message -----
> On 09/05/2014 08:15 PM, Nathan Scott wrote:
> > [ ... ]
> > 2. Many PMDAs (including "core" PMDAs) have both daemon & DSO
> > variants which duplicate a bit of code (hence increasing the
> > installed package size ondisk).  I wonder if we could move to
> > a model where the daemon PMDAs in such cases use the run-time
> > DSO, instead of linking with the .o at build time?  (this'll
> > need a new libpcp_pmda helper function to wrap the dlopen(3)
> > call).
> 
> That could work. Another idea could be to only ship the DSO
> variant for some PMDAs, which would be preferable to shipping
> only the daemon - for local context support.

*nod* - in the past, the other advantage of having daemon is you
can isolate PMDA performance analysis to the individual process
(pmdalinux has been beaten with this stick a number of times).

> We could add a new PMDA_INTERFACE version that supports e.g.
> FOO_args(argc, argv) or perhaps an extended FOO_init() that has
> support for args, something like that. PMDAs that need arguments

Yep, interesting approach - that'd tackle a DSO PMDA limitation
in the process - bonus.

> (such as the logger PMDA) could then be DSOs, which would be a
> step closer to a viable pmlogger that only uses a local context
> (no pmcd required for a minimal logging deployment).

Yeah.  Hey - on that, I was thinking about revving the pmlogger
control file format recently to help out local-context-pmlogger
for the case where DSO PMDAs need to run as root.  We currently
have a pmsocks column, bit-rotting away nicely - maybe we could
reclaim that (v1.2 format) and make it mean "run pmlogger under
sudo" instead?

cheers.

--
Nathan

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