linux-kernel - Re: [PATCH 3/7] lockdep: lock contention tracking

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Message-Id: <1179932865.7019.90.camel@twins>
Date:	Wed, 23 May 2007 17:07:45 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Jason Baron <jbaron@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Bill Huey <billh@...ppy.monkey.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 3/7] lockdep: lock contention tracking

On Wed, 2007-05-23 at 10:40 -0400, Jason Baron wrote:
> On Wed, 23 May 2007, Peter Zijlstra wrote:
> 
> > Count lock contention events per lock class. Additionally track the first four
> > callsites that resulted in the contention.
> > 
> 
> I think that we need the total number of locking calls, not just the total 
> number of *contended* locking calls, in order to make the data 
> significant. Same for waittime. Yes, this pollutes the fastpath. In the 
> contention case, its one extra addition, and for the waittime, its a call 
> the sched_clock(). I don't think that's too much to pay for much more 
> meaningful data.

The holdtime statistics add these numbers.

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