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Re: PAPI pmda Note

To: "Frank Ch. Eigler" <fche@xxxxxxxxxx>, Lukas Berk <lberk@xxxxxxxxxx>
Subject: Re: PAPI pmda Note
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Wed, 17 Sep 2014 19:28:32 -0400 (EDT)
Cc: pcp@xxxxxxxxxxx
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <y0megvaas2h.fsf@xxxxxxxx>
References: <20140905200756.GA31071@xxxxxxxxxx> <214253475.50237185.1410857725513.JavaMail.zimbra@xxxxxxxxxx> <87fvfr5ipk.fsf@xxxxxxxxxx> <1161038122.50704119.1410924350821.JavaMail.zimbra@xxxxxxxxxx> <y0megvaas2h.fsf@xxxxxxxx>
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Thread-index: 5A14Cw7IIeilAtD60HaaZgK37s6lFg==
Thread-topic: PAPI pmda Note

----- Original Message -----
> Nathan Scott <nathans@xxxxxxxxxx> writes:
> 
> > [...]  OOC, is it possible to ask PAPI what hardware counters are
> > enabled?  (IOW, without relying on the state kept in-memory, in the
> > daemon, as a result of changes it made itself, but rather by asking
> > the hardware/kernel?).
> 
> No - the kernel keeps that info to itself, and multiplexes amongst
> applications and its own internal usage.
> 

Ah well, that's a shame.

> 
> > If so, that would be great to use as the value for the control "enable"
> > metric,
> 
> (I've nudged lberk toward using the ".status" read-only metric as a
> better-colored toolshed to describe current state.)
> 
> > instead of simply exporting whatever state changes we've made in the
> > PMDA (and assuming everything was disabled when it started, which
> > may not have been the case). [...]
> 
> (I've nudged lberk toward not making ".enable"/".disable" readable at
> all, especially if they are to return merely the most-recent deltas
> rather than the cumulative situation.)
> 

*nod* - sounds good.

cheers.

--
Nathan

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