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    SubjectRe: [PATCH] VFS: br_write_lock locks on possible CPUs other than online CPUs
    On Thu, Dec 22, 2011 at 08:08:56AM +0000, Al Viro wrote:
    > On Wed, Dec 21, 2011 at 11:20:47PM -0800, Andrew Morton wrote:
    > > On Thu, 22 Dec 2011 07:02:15 +0000 Al Viro <viro@ZenIV.linux.org.uk> wrote:
    > >
    > > > On Wed, Dec 21, 2011 at 02:12:29PM -0800, Andrew Morton wrote:
    > > > > off-topic, but the lockdep stuff in include/linux/lglock.h
    > > > > (LOCKDEP_INIT_MAP and DEFINE_LGLOCK_LOCKDEP) appears to be dead code.
    > > >
    > > > Um? See ..._lock_init(); it's used there.
    > >
    > > oops, I had Andi's patch applied.
    > >
    > > Wanna take a look at it while things are fresh in your mind?
    >
    > a) tons of trivial conflicts with fs/namespace.c changes in my tree
    > b) more seriously, the question of overhead - see the mail you replied
    > to.
    >

    The costly operations here are the atomics and nothing really changes
    for them. So I don't expect any measurable difference.

    I actually have an idea to remove them for the common case, but not in
    that patchkit or cycle :)

    I can run a ftrace if you want, but I expect any difference to be below
    the measurement inaccuracy.

    -Andi

    --
    ak@linux.intel.com -- Speaking for myself only.


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