Re: [PATCH 2/2] locking/mutex,rwsem: Reduce vcpu_is_preempted() calling frequency

From: Peter Zijlstra
Date: Wed Feb 08 2017 - 14:58:58 EST

On Wed, Feb 08, 2017 at 01:00:25PM -0500, Waiman Long wrote:
> As the vcpu_is_preempted() call is pretty costly compared with other
> checks within mutex_spin_on_owner() and rwsem_spin_on_owner(), they
> are done at a reduce frequency of once every 256 iterations.

That's just disgusting.