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

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Message-ID: <Pine.LNX.4.64.0705231035270.22023@dhcp83-20.boston.redhat.com>
Date:	Wed, 23 May 2007 10:40:59 -0400 (EDT)
From:	Jason Baron <jbaron@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
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, 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.

thanks,

-Jason
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