Hi,
On 2015-04-20 14:22, Nathan Scott wrote:
>>
>> please see below for a proposal for a new process level PMDA.
>>
>> There are other related PMDAs already (at least hotproc, linux_proc,
>> and process) but I think this one complements the offering nicely
>> with the ability to easily monitor certain processes (e.g., just say
>> $procs = 'java' on the fly to start monitoring all java processes
>> regardless of their PIDs) and also by providing e.g. per-process
>> IO stats which are not easily (if at all) available from other PMDAs.
>
> It sounds like there's alot of overlap here with hotproc.* - pmdaproc
> nowadays provides hotproc.* metrics, thanks to Martins recent efforts,
hmm, which hotproc are we talking about? When looking at
src/pmdas/hotproc, I don't see any notable recent changes, copyright
dates are mostly from the previous millennium. Hmm, perhaps you are
referring to linux_proc/hotproc.c which seems to have received updates
recently?
> which may not be widely known yet (not really following the advantage
> to parsing pidstat over accessing proc.* via hotproc ... am I missing
> something subtle there?).
Btw, a general question, is there a way to access other metrics from
PMDA? (Think of writing a PMDA which would provide custom metrics under
"foo." but some special metrics would be calculated with help of some
external metric like hinv or so.)
> Those new hotproc.* metrics do allow both a configuration file-based
> mechanism (like this new PMDA) & also support a very dynamic pmstore
> update model too, like:
>
> # pmstore hotproc.control.config 'fname = "java"'
>
> to set the process filtering on-the-fly (the above syntax may not be
> 100% correct, thats just from memory - it'll be close though).
Ok, I wasn't aware of this, would be great to know how to do that, the
above example doesn't seem to work and the pmdahotproc.1 man isn't
really that helpful.
> Is there something missing from the hotproc.* metrics that this new
> PMDA would provide Marko? I don't really follow the IO-stats comment
> - there's no magic that pidstat can do that pmdaproc cannot AFAIK in
> terms of querying the kernel for stats.
The reason for using pidstat was mainly that it was quick to write the
PMDA. As a bonus it also provided those read/s and write/s metrics which
I didn't see readily available elsewhere.
> From a quick look, the docs for the (recently-added-to-Linux) hotproc
> metrics could be improved - Martins, could we find a way to report
> help text for hotproc.control, hotproc.predicate, and hotproc.total?
> And the pmdaproc(1) man page is a bit lacking in coverage of how to
> use hotproc. Maybe a tutorial page would suit here too?
Yes, that would be great. The use case I was thinking for the pidstat
PMDA was that it would be suitable almost anyone to add certain
processes to be monitored without necessarily knowing anything about
PCP. For pidstat the required documentation to achieve this was more or
less those two lines in the configuration file.
Thanks,
--
Marko Myllynen
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