Re: [RFC PATCH-tip v2 2/6] locking/rwsem: Stop active read lock ASAP

On 06/15/2016 10:14 PM, Davidlohr Bueso wrote:

On Wed, 15 Jun 2016, Waiman Long wrote:

quoted

I think there will be a little bit of performance impact for a workload that produce just the right amount of rwsem contentions.

I'm not saying the change doesn't make sense, but this is the sort of
thing that will show nice numbers in one workload and go bite you in
another.

Thanks,
Davidlohr

I would certainly agree if the additional atomic op is in the fastpath. Since it is in the slowpath, one additional atomic op will just be a small part of the whole rwsem_down_read_failed() function. I doubt if the performance degradation, if any, can be even noticeable.

Cheers,
Longman