linux-kernel - Re: [PATCH 10/11] tracing/perf: Fix lock events recursions in the fast path

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Message-ID: <1265371808.22001.502.camel@laptop>
Date:	Fri, 05 Feb 2010 13:10:08 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>, paulmck@...ux.vnet.ibm.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul Mackerras <paulus@...ba.org>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Li Zefan <lizf@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 10/11] tracing/perf: Fix lock events recursions in the
 fast path

On Fri, 2010-02-05 at 11:49 +0100, Ingo Molnar wrote:
> 
> > That said, I'm not at all happy about removing lockdep annotations to make 
> > the tracer faster, that's really counter productive.
> 
> Are there no dynamic techniques that could be used here?
> 
> Lockdep obviously wants maximum instrumentation coverage - performance be 
> damned.
> 
> Lock profiling/tracing/visualization wants the minimum subset of events it is 
> interested in - everything else is unnecessary overhead.

Well, they could start by moving the tracepoint inside the lockdep
recursion check.

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