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    SubjectRe: 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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