Re: [Qemu-devel] [PATCH 0/7] x86: Rework KVM-defaults compat code, enable kvm_pv_unhalt by default

[Waiman Long]

On 10/10/2017 11:50 AM, Eduardo Habkost wrote:
>> Yes.  Another possibility is to enable it when there is >1 NUMA node in
>> the guest.  We generally don't do this kind of magic but higher layers
>> (oVirt/OpenStack) do.
> Can't the guest make this decision, instead of the host?

By guest, do you mean the guest OS itself or the admin of the guest VM?

I am thinking about maybe adding kernel boot command line option like
"unfair_pvspinlock_cpu_threshold=4" which will instruct the OS to use
unfair spinlock if the number of CPUs is 4 or less, for example. The
default value of 0 will have the same behavior as it is today. Please
let me know what you guys think about that.

Cheers,
Longman