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

2017-02-08 Thread Waiman Long
On 02/08/2017 02:05 PM, Peter Zijlstra wrote: > 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

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

2017-02-08 Thread Peter Zijlstra
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.

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

2017-02-08 Thread Waiman Long
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. Signed-off-by: Waiman Long --- kernel/locking/mutex.c | 5 -