linux-kernel - Re: [PATCH 6/7] perf, x86: Example code for AMD IBS

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Message-ID: <1312281474.1147.40.camel@twins>
Date:	Tue, 02 Aug 2011 12:37:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Robert Richter <robert.richter@....com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Michael Cree <mcree@...on.net.nz>,
	Lin Ming <ming.m.lin@...el.com>
Subject: Re: [PATCH 6/7] perf, x86: Example code for AMD IBS

On Mon, 2011-08-01 at 07:50 +0200, Robert Richter wrote:
> On 29.07.11 12:58:49, Peter Zijlstra wrote:
> > On Thu, 2011-07-28 at 15:46 +0200, Robert Richter wrote:
> > >  tools/perf/Documentation/examples/ibs.c    |  436 ++++++++++++++++++++++++++++
> > 
> > That really isn't the place for this..
> > 
> > Also, how similar is the Alpha PMU to AMD IBS?
> 
> Would you prefer
> 
>  tools/perf/Documentation/examples/x86/ibs.c
> 
> instead?

Possibly, but having just looked at the example again I don't really see
it doing anything perf-record doesn't already do, so why does it deserve
to live at all?

Initially I thought it was a record+report like example, some code
interpreting the 'mess' that comes out of IBS would be most appreciated
and I think we can even ship that as perf-ibs-report/perf-ibs-annotate
or so (and if its still remotely similar to its Alpha precursor that
might make the Alpha folks happy too).

> Actually I wasn't sure if this place is ok at all. But I wanted to
> publish the code for reference and testing. There isn't somthing
> similar already there, and the perf tool code is also not the best
> place to implement such cpu specific features.
> 
> But putting it to the documentation is common practice for library
> packages (e.g. libpapi and libpfm). If the example is not for the
> given architecture it won't be added to the package documentation.
> This example won't be installed at all. Even for very special features
> an example is important since it is often not part of the generic
> implementation.

Right, its just that I'm not seeing the extra value at all, aside from
maybe the IBS_*_DEFAULT values that should live as an event config
(poking mlin to see where he's at with those patches..).
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