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

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Message-ID: <w2v520f0cf11004230131i743c596emfd0e5b8870330a8b@mail.gmail.com>
Date:	Fri, 23 Apr 2010 10:31:16 +0200
From:	John Kacur <jkacur@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Yong Zhang <yong.zhang@...driver.com>,
	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 10:05 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, 2010-04-23 at 09:24 +0200, John Kacur wrote:
>> direct dependencies:                  8752 [max: 16384]
>> I have
>> stack-trace invocations: 10888
>> from the same run.
>>
>> Still trying to figure out what the meaning is of that though to be
>> honest.
>>
>> Here is a portion of the lockdep_stats, with all of the new fields and the
>> redundant ones.
>>
>> stack-trace invocations: 10888
>>         LOCK_USED_IN_HARDIRQ: 15
>>         LOCK_USED_IN_HARDIRQ_READ: 0
>>         LOCK_ENABLED_HARDIRQ: 543
>>         LOCK_ENABLED_HARDIRQ_READ: 28
>>         LOCK_USED_IN_SOFTIRQ: 0
>>         LOCK_USED_IN_SOFTIRQ_READ: 0
>>         LOCK_ENABLED_SOFTIRQ: 543
>>         LOCK_ENABLED_SOFTIRQ_READ: 28
>>         LOCK_USED_IN_RECLAIM_FS: 5
>>         LOCK_USED_IN_RECLAIM_FS_READ: 0
>>         LOCK_ENABLED_RECLAIM_FS: 95
>>         LOCK_ENABLED_RECLAIM_FS_READ: 8
>>         LOCK_USED: 871
>
> 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)
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