Messages in this thread | | | Date | Mon, 25 Nov 2013 20:52:23 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 4/5] futex: Avoid taking hb lock if nothing to wakeup |
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On Mon, 25 Nov 2013, Davidlohr Bueso wrote: > On Mon, 2013-11-25 at 18:32 +0100, Thomas Gleixner wrote: > > If the smp_mb() is heavy weight, then it will hurt massivly in the > > case where the hash bucket is not empty, because we add the price for > > the smp_mb() just for no gain. > > > > In that context it would also be helpful to measure the overhead on > > x86 for the !empty case. > > Absolutely, I will add these comparisons. If we do notice that we end up > hurting the !empty case, would the current patch using atomic ops still > be considered? We have made sure that none of the changes in this set > affects performance on other workloads/smaller systems.
Please read my last reply to the atomic ops approach.
Aside of that we need numbers for a significant range of !x86.
Thanks,
tglx
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