On Mon, 2009-01-12 at 19:32 +0200, Avi Kivity wrote: > Peter Zijlstra wrote: > > Spinlocks can use 'pure' MCS locks. > > > > How about this, then. In mutex_lock(), keep wait_lock locked and only > release it when scheduling out. Waiter spinning naturally follows. If > spinlocks are cache friendly (are they today?)
(no they're not, Nick's ticket locks still spin on a shared cacheline IIRC -- the MCS locks mentioned could fix this) > we inherit that. If > there is no contention on the mutex, then we don't need to reacquire the > wait_lock on mutex_unlock() (not that the atomic op is that expensive > these days). That might actually work, although we'd have to move the __mutex_slowpath_needs_to_unlock() branch outside wait_lock otherwise we'll deadlock :-) It might be worth trying this if we get serious fairness issues with the current construct. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
