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

On 02/08/2017 02:05 PM, Peter Zijlstra wrote:

On Wed, Feb 08, 2017 at 01:00:25PM -0500, Waiman Long wrote:

quoted

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.

I do have some doubt myself on the effectiveness of this patch. Anyway,
it is the first patch that I think is more beneficial.

Cheers,
Longman