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    SubjectRe: [GIT PULL] adaptive spinning mutexes
    On Thu, Jan 15, 2009 at 10:16:53AM -0800, Linus Torvalds wrote:
    >
    >
    > On Thu, 15 Jan 2009, Ingo Molnar wrote:
    > >
    > > btw., i think spin-mutexes have a design advantage here: in a lot of code
    > > areas it's quite difficult to use spinlocks - cannot allocate memory,
    > > cannot call any code that can sporadically block (but does not _normally_
    > > block), etc.
    > >
    > > With mutexes those atomicity constraints go away - and the performance
    > > profile should now be quite close to that of spinlocks as well.
    >
    > Umm. Except if you wrote the code nicely and used spinlocks, you wouldn't
    > hold the lock over all those unnecessary and complex operations.
    >
    > IOW, if you do pre-allocation instead of holding a lock over the
    > allocation, you win. So yes, spin-mutexes makes it easier to write the
    > code, but it also makes it easier to just plain be lazy.

    In infrequently invoked code such as some error handling, lazy/simple
    can be a big win.

    Thanx, Paul


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