Re: [PATCH v3 0/3] KVM: Yield to IPI target if necessary

From: Wanpeng Li
Date: Tue Jun 11 2019 - 06:30:28 EST

On Mon, 10 Jun 2019 at 22:34, Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx> 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 will extend irq disabled time in __send_ipi_mask(). In addition,
sched yield can be used to optimize other synchronization primitives
in guest I think.

Wanpeng Li