On 8/24/22 17:26, Sean Christopherson wrote:
I say "if", because I think this needs to come with performance numbers to show the impact on guest latency so that KVM and its users can make an informed decision. And if it's unlikely that anyone will ever want to enable TPAUSE for halt polling, then it's not worth the extra complexity in KVM.
Yeah, halt polling works around perhaps the biggest performance issue with VMs compared to bare metal (so much that it's even possible to move halt polling _inside_ the guest for extra performance).
I am ready to be proven wrong but I doubt TPAUSE will have a small effect, and if one wants the most power saving they should disable halt polling. Perhaps KVM could do it automatically if the powersaving governor is in effect?
Paolo
