Re: [PATCH] x86/kvm: Don't use pvqspinlock code if only 1 vCPU

[Waiman Long]

On 07/18/2018 09:15 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 17, 2018 at 05:59:27PM -0400, Waiman Long wrote:
>> On a VM with only 1 vCPU, the locking fast path will always be
>> successful. In this case, there is no need to use the the PV qspinlock
>> code which has higher overhead on the unlock side than the native
>> qspinlock code.
> Why not make this global? That is for both KVM and Xen and any
> other virtualized guest that uses this?

Right, I will send another patch for Xen. The pvqspinlock code has to be
explicitly opted in. Right now, both Xen and KVM used it in the tree. I
am not sure about other out-of-tree modules. There is nothing I can do
for those.

Cheers,
Longman