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

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Message-ID: <1265455442.30057.499.camel@laptop>
Date:	Sat, 06 Feb 2010 12:24:02 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Lai Jiangshan <laijs@...fujitsu.com>,
	paulmck@...ux.vnet.ibm.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 Sat, 2010-02-06 at 12:12 +0100, Frederic Weisbecker wrote:

> That said, I think this is good for a first step, but we can't continue
> to force the lock events -> lockdep dependency in the long term. We
> can't have a serious lock profiling if we are doomed to suffer the
> slowness due to lockdep checks at the same time.
> 
> Sure we can continue to support having both, but I think we should also
> think about a solution to handle lock events without it in the future.
> That will require some minimal lockdep functionalities (keeping the
> lockdep map, and class hashes).

You mean like building without CONFIG_PROVE_LOCKING, or boot with
lockdep.prove_locking=0, or use echo 0
> /sys/modules/lockdep/prove_locking ?

That keeps the lock tracking but does away with all the dependency
analysis and was created for just such an use case as you are looking
at, namely lockstat.

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