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RFC: papi pmda auto-enable on fetch

To: pcp developers <pcp@xxxxxxxxxxx>
Subject: RFC: papi pmda auto-enable on fetch
From: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
Date: Mon, 3 Nov 2014 16:07:47 -0500
Delivered-to: pcp@xxxxxxxxxxx
User-agent: Mutt/1.4.2.2i
Hi -

Please have a look over pcpfans.git fche/papi.  If it looks generally
acceptable, I'm ready to assist lberk in QA'ing the heck out of it.


commit 3f7223221fc313441079be7c8c41c3d14a322247
Author: Frank Ch. Eigler <fche@xxxxxxxxxx>
Date:   Mon Nov 3 15:55:41 2014 -0500

    papi pmda: add counter auto-enable on fetch
    
    By reinterpreting the papi_info[].metric_enabled as a timestamp rather
    than a boolean, and a small bit of logic, we get automatic enablement
    of PAPI metric/counters upon pmfetch.  This allows PAPI metrics to be
    used with plain old pmlogger, pmval, etc., without necessary manual
    pmstore's.  Counters are retired based on a timeout mechanism,
    assisted by pmaf(3).  The papi.control.status metric is enhanced to
    show the remaining lifespan of the counters, and to make it more safe
    & reliable.
    
    A new papi.control.auto_enable metric is available to set the timeout
    (default 120 seconds).  The Install script runs a papi.control.reset
    operation to avoid leaving the counters running for even that long
    after the post-install metric/value checks.
    
    The previous pmstore mechanism is left in place unchanged, and
    overrides the automatic scheme.

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