Messages in this thread | | | Date | Mon, 10 Sep 2018 10:15:50 -0700 | From | Davidlohr Bueso <> | Subject | Re: [PATCH] locking/rwsem: Make owner store task pointer of last owning reader |
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On Mon, 10 Sep 2018, Waiman Long wrote:
>One major issue with a combined count/owner is that we may have to use >cmpxchg for reader lock which will certainly impact reader-heavy >workloads. I have also thought about ways to compress the task pointer >address so that it can use fewer bits and leave the rests for reader >count. It is probably doable on 64-bit systems, but likely not on 32-bit >system given that there are less bits to play around.
Yeah we've discussed this before. As a cleanup it would obviously be good, but I fear about raw performance loss when using cmpxchg instead of xadd.
Thanks, Davidlohr
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