Messages in this thread | | | Date | Thu, 20 Apr 2017 19:53:50 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock |
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On Thu, Apr 20, 2017 at 10:13:26AM -0700, Davidlohr Bueso wrote:
> I have thought of some heuristics for avoiding sleeping under certain > constraints, which could mitigate the spinning step we loose, but I fear it > will never be exactly as fast as rwsems -- just consider > we always take the tree->lock.
But tree->lock is a spinlock, so while this gets us out of rwsem-xadd territory for the fast paths, the whole lock-stealing and optimistic spinning stuff is on a different scale.
Those are about avoiding actually going to sleep and having to be woken up (and waiting to become running) again, which is a long time.
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