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

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Message-ID: <20110512122658.GB3639@zhy>
Date:	Thu, 12 May 2011 20:26:58 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	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 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 :)

Cc'ing PeterZ and Ingo.

Thanks,
Yong
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