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    SubjectRe: [patch 0/3] j_state_lock, j_list_lock, remove-bitlocks

    On Wed, 16 Mar 2005, Ingo Molnar wrote:

    > * Andrew Morton <> wrote:
    > >
    > > ooh, I'd rather not. I spent an intense three days removing all the
    > > sleeping locks from ext3 (and three months debugging the result).
    > > Ended up gaining 1000% on 16-way.
    > >
    > > Putting them back in will really hurt the SMP performance.
    > ah. Yeah. Sniff.
    > if we gain 1000% on a 16-way then there's something really wrong about
    > semaphores (or scheduling) though. A semaphore is almost a spinlock, in
    > the uncontended case - and even under contention we really (should) just
    > spend the cycles that we'd spend spinning. There will be some
    > intermediate contention level where semaphores hurt, but 1000% sounds
    > truly excessive.

    Could it possibly be that in the process of removing all the sleeping
    locks from ext3, that Andrew also removed a flaw in ext3 itself that is
    responsible for the 1000% improvement?

    -- Steve

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