linux-kernel - [BUG] perf_event: inst_retired:any_p:c=16:i=1 is not equivalent to cpu_clk_unhalted:thread

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Message-ID: <AANLkTinVc=VRo+2=M3x5HEoF__SOJn7kBk7Ek0R94TG9@mail.gmail.com>
Date:	Tue, 18 Jan 2011 19:05:12 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>, mingo@...e.hu,
	Lin Ming <ming.m.lin@...el.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: [BUG] perf_event: inst_retired:any_p:c=16:i=1 is not equivalent to cpu_clk_unhalted:thread_p

Peter,

commit 7639dae0ca11038286bbbcda05f2bef601c1eb8d
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Tue Dec 14 21:26:40 2010 +0100

    perf, x86: Provide a PEBS capable cycle event



Even with the transformation cmask=16:invert=1, you are not quite
counting the same thing.

inst_retired:any_p:c=16:i=1  is different from cpu_clk_unhalted:thread_p

Simply because, I think, this form of inst_retired counts in HALTED state.

This automatic transformation would be "okay" in per-thread mode, but
not in system-wide mode. It should not be done under the cover. I would
rather have this option at the user level.
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