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Calculated/derived metrics?

To: pcp@xxxxxxxxxxx
Subject: Calculated/derived metrics?
From: Marko Myllynen <myllynen@xxxxxxxxxx>
Date: Mon, 04 May 2015 11:18:08 +0300
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Organization: Red Hat
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Hi,

On 2015-04-21 15:43, Marko Myllynen wrote:
>>>
>> I think those will be the values behind the proc.io.* metrics, FWIW, but
>> have not checked closely (see e.g. /proc/self/io).
> 
> Yes, the values are basically proc.io.{read,write}_bytes / process
> lifetime-in-seconds. So it's a calculated / pre-processed value which
> quickly gives an idea of a process IO activity at a time. (See below for
> more on this.)
> 
> Wrt usability in general, the above mentioned metrics read/s and write/s
> can of course be calculated based on the process lifetime and read/write
> totals so far. But if using something like pmval to quickly check what
> the process is up to at the moment, you don't get that sort of idea
> instantly.
> 
> This is of course not specific to monitoring processes but applies in
> general, what's the best practice to follow a metric which actually is a
> combination or calculation of two or more metrics being collected?

I think it would still be interesting to hear experiences around this,
if calculated/derived metrics are needed in some cases, how to get them
most efficiently?

Thanks,

-- 
Marko Myllynen

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