On Mon, Jun 10, 2019 at 04:34:20PM +0200, Radim Krčmář wrote: > 2019-05-30 09:05+0800, Wanpeng Li: > > The idea is from Xen, when sending a call-function IPI-many to vCPUs, > > yield if any of the IPI target vCPUs was preempted. 17% performance > > increasement of ebizzy benchmark can be observed in an over-subscribe > > environment. (w/ kvm-pv-tlb disabled, testing TLB flush call-function > > IPI-many since call-function is not easy to be trigged by userspace > > workload). > > Have you checked if we could gain performance by having the yield as an > extension to our PV IPI call? > > It would allow us to skip the VM entry/exit overhead on the caller. > (The benefit of that might be negligible and it also poses a > complication when splitting the target mask into several PV IPI > hypercalls.) Tangetially related to splitting PV IPI hypercalls, are there any major hurdles to supporting shorthand? Not having to generate the mask for ->send_IPI_allbutself and ->kvm_send_ipi_all seems like an easy to way shave cycles for affected flows.