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Date: Tue, 8 Nov 2011 13:15:01 +0100
From: Ingo Molnar <mingo@elte.hu>
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Subject: Re: [Qemu-devel] [F.A.Q.] perf ABI backwards and forwards
	compatibility
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To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Alexander Graf <agraf@suse.de>, Ted Ts'o <tytso@mit.edu>, Peter Zijlstra <a.p.zijlstra@chello.nl>, "kvm@vger.kernel.org list" <kvm@vger.kernel.org>, qemu-devel Developers <qemu-devel@nongnu.org>, Vince Weaver <vince@deater.net>, "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>, Pekka Enberg <penberg@kernel.org>, Blue Swirl <blauwirbel@gmail.com>, "Frank Ch. Eigler" <fche@redhat.com>, Arnaldo Carvalho de Melo <acme@redhat.com>, Avi Kivity <avi@redhat.com>, =?iso-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>, Linus Torvalds <torvalds@linux-foundation.org>


* Pekka Enberg <penberg@cs.helsinki.fi> wrote:

> [...] There's an easy fix for this too: improve "perf test" to 
> cover the cases you're intested in. While ABI spec would be a nice 
> addition, it's not going to make compatibility problems magically 
> go away.

Yes, exactly - 'perf test' has been written with that exact purpose. 
In practice 'perf' will cover almost all parts of the ABI.

The one notable thing that isnt being tested in a natural way is the 
'group of events' abstraction - which, ironically, has been added on 
the perfmon guys' insistence. No app beyond the PAPI self-test makes 
actual use of it though, which results in an obvious lack of testing.

Vince: the code is in tools/perf/builtin-test.c and our offer still 
stands, feel free to extend it. Maybe there's some other volunteer 
willing to do that?

Thanks,

	Ingo