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    SubjectRe: [PATCH 01/11] quota: Improve locking
    On Fri 23-01-09 23:49:12, Andrew Morton wrote:
    > On Fri, 16 Jan 2009 19:08:09 +0100 Jan Kara <jack@suse.cz> wrote:
    >
    > > static DEFINE_SPINLOCK(dq_list_lock);
    > > +static DEFINE_SPINLOCK(dq_state_lock);
    > > DEFINE_SPINLOCK(dq_data_lock);
    >
    > The chances are very good that two or even three of these locks will
    > all get placed into the same cacheline in main memory. The effects
    > will be quite bad if different CPUs (or, worse, different nodes) are
    > taking these locks.
    >
    > For single, kernel-wide locks like these I think we should almost
    > always pad out to a cacheline.
    I never thought about this. Thanks for the idea.

    > With __cacheline_aligned_in_smp, rather than __cacheline_aligned.
    > Because spinlocks do take space even in uniprocessor builds.
    I've added this to my list of quota cleanups.

    Honza
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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