linux-kernel - Re: [PATCH] lockdep: Add nr_save_trace

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Message-ID: <o2v520f0cf11004230240ubcdabe13ufba29de626d6b40b@mail.gmail.com>
Date:	Fri, 23 Apr 2010 11:40:52 +0200
From:	John Kacur <jkacur@...hat.com>
To:	Yong Zhang <yong.zhang@...driver.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Clark Williams <williams@...hat.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gregory Haskins <ghaskins@...ell.com>
Subject: Re: [PATCH] lockdep: Add nr_save_trace_invocations counter

On Fri, Apr 23, 2010 at 10:49 AM, Yong Zhang <yong.zhang@...driver.com> wrote:
> On Fri, Apr 23, 2010 at 10:31:16AM +0200, John Kacur wrote:
>> > 8752+871+8+95+5+28+543+28+543+15=10888
>> >
>> > So you get a stack-trace for each direct-dependency, and you get a
>> > stack-trace for each LOCK_state, the sum seems to match the total
>> > invocations.
>> >
>> > Non of these numbers look strange..
>> >
>>
>> As I told Peter privately the laptop that triggered the
>> MAX_STACK_TRACE_ENTRIES every time, has met an
>> unfortunate early demise. However, I think it was the config - not the
>> hardware. On this machine where the above
>> numbers come from, I believe I have less debug options configured -
>> but it is running the exact same kernel as
>> the laptop was. (2.6.33.2-rt13)
>
> Through a rough computation:
> MAX_STACK_TRACE_ENTRIES/10888 = 24
> That means the average stack deepth is about 24.
> So I'm thinking if we can take a check on the biggest deepth?
> Could this make sense?
>

Hi Yong, yes that makes sense, I'll see if I can provide a patch for that too.

Thanks
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