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    SubjectRe: [git pull] scheduler fixes

    * Matthew Wilcox <matthew@wil.cx> wrote:

    > > > Current XFS CVS has a fix from myself and Christoph that gets rid
    > > > of the l_flushsema and replaces it with a staggered wakeup of each
    > > > task that's waiting as the previously woken task clears the
    > > > critical section.
    > >
    > > the solution is to reduce semaphore usage by converting them to
    > > mutexes. Is anyone working on removing legacy semaphore use from
    > > XFS?
    >
    > This race is completely irrelevant to converting semaphores to
    > mutexes. [...]

    i was not talking about the race. I was just reacting on your comments
    about thundering herds and staggered wakeups - which is a performance
    detail. Semaphores should not regress AIM7 by 50% but otherwise they are
    legacy code and their use should be reduced monotonically, so i was
    asking why anyone still cares about tuning semaphore details in XFS
    instead of just working on removing semaphore use from them.

    > [...] It can only occur for semaphores which /can't/ be converted to
    > mutexes.

    exactly what usecase is that? Perhaps it could be converted to an atomic
    counter + the wait_event() APIs.

    Ingo


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