linux-kernel - Re: perf, x86: Provide a PEBS capable cycle event

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Message-ID: <20110126113740.GA13911@elte.hu>
Date:	Wed, 26 Jan 2011 12:37:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: perf, x86: Provide a PEBS capable cycle event


* Linux Kernel Mailing List <linux-kernel@...r.kernel.org> wrote:

> Gitweb:     http://git.kernel.org/linus/7639dae0ca11038286bbbcda05f2bef601c1eb8d
> Commit:     7639dae0ca11038286bbbcda05f2bef601c1eb8d
> Parent:     abe43400579d5de0078c2d3a760e6598e183f871
> Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
> AuthorDate: Tue Dec 14 21:26:40 2010 +0100
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Thu Dec 16 11:36:44 2010 +0100
> 
>     perf, x86: Provide a PEBS capable cycle event
>     
>     Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>     LKML-Reference: <new-submission>
>     Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  arch/x86/kernel/cpu/perf_event_intel.c |   26 ++++++++++++++++++++++++++
>  1 files changed, 26 insertions(+), 0 deletions(-)

btw., precise profiling via PEBS:

  perf record -e cycles:p ...

works pretty nicely now on Nehalem CPUs and later.

Could we perhaps make perf record and perf top default to cycles:p on x86, and 
silently fall back to regular cycles events if the CPU does not support this event 
type?

That would make our profiles more precise by default - without users having to do 
anything funky.

Thanks,

	Ingo
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