Messages in this thread | | | Subject | Re: [RFC patch 0/5] futex: Allow lockless empty check of hashbucket plist in futex_wake() | From | Davidlohr Bueso <> | Date | Tue, 26 Nov 2013 06:49:59 -0800 |
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On Tue, 2013-11-26 at 12:56 +0100, Peter Zijlstra wrote: > On Tue, Nov 26, 2013 at 12:21:40PM +0100, Ingo Molnar wrote: > > I'm somewhat reluctant to chalk it up to a single mfence - maybe > > timings/behavior changed in some substantial way?
That would be nthread mfence calls.
> > Ah indeed! We also changed the case where an enqueueing futex sees the > uval change and bails. It is now far more expensive due to having to > both queue and unqueue, whereas before it wouldn't queue at all.
Right, but those particular numbers do not measure that path.
Thanks, Davidlohr
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