Messages in this thread | | | Subject | Re: [PATCH -v8][RFC] mutex: implement adaptive spinning | From | Peter Zijlstra <> | Date | Wed, 14 Jan 2009 17:46:39 +0100 |
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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.
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