linux-kernel - Re: lock_stat &rq->lock/1 class name meaning

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Message-ID: <BANLkTim1pGQvGwvM09C0LCkYwmDP3uFB2Q@mail.gmail.com>
Date:	Thu, 12 May 2011 22:22:57 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Juri Lelli <juri.lelli@...il.com>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: lock_stat &rq->lock/1 class name meaning

On Thu, May 12, 2011 at 8:26 PM, Yong Zhang <yong.zhang0@...il.com> wrote:
> On Thu, May 12, 2011 at 02:11:02PM +0200, Juri Lelli wrote:
>> Thanks!
>>
>> On 05/12/2011 12:57 PM, Yong Zhang wrote:
>> >On Wed, May 11, 2011 at 06:26:10PM +0200, Juri Lelli wrote:
>> >>Hi,
>> >>I'm trying to collect contention statistics through /proc/lock_stat
>> >>about scheduler data structures.
>> >>
>> >>What I obtain if a do "cat /proc/lock_stat" is something like:
>> >>...
>> >>&rq->lock:         13128          13128           0.43
>> >>[...]
>> >>
>> >>I guess the first one is about the per-rq (per-CPU) spinlock, but
>> >>what about the second? What the "/1" stands for?
>> >
>> >It is also rq but it's subclass is 1.
>> >
>> >Take a look at raw_spin_lock_nested(&this_rq->lock, SINGLE_DEPTH_NESTING);
>> >in _double_lock_balance()
>>
>> Ok, I've put more light on this also looking at lockdep.h comments
>> and lockdep-design documentation.
>>
>> Since I'm probably not the only one having troubles undestanding
>> lock_stat output, maybe could be useful to add something on this
>> inside lockstat documentation (I can try to do this). What you
>> think?
>
> Any improvement will be good :)

I think Documentation/lockstat.txt is out of date,
the last change of this file can be back to
Thu Nov 19 13:54:05 2009.
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