On 11/08/20 04:04, Wanpeng Li wrote: > We found that the IPI broadcast latency in the guest when AVIC=1, > exposing xapic is worse than when AVIC=0, exposing xapic. The host is > AMD ROME, 2 sockets, 96 cores, 192 threads, the VM is 180 vCPUs. The > guest boots with kvm-hint-dedicated=on, --overcommit cpu-pm=on, -smp > 180,sockets=2,cores=45,threads=2, l3-cache=on qemu command-line, the > pCPU which vCPU is running on is isolated. Both the guest and host > kernel are 5.8 Linus' tree. (Note, if you fails to boot with > --overcommit cpu-pm=on, you can comments out commit e72436bc3a52, I > have a report here, https://lkml.org/lkml/2020/7/8/308) > > IPI microbenchmark(https://lkml.org/lkml/2017/12/19/141, Destination > Shorthand is All excluding self) > > avic0_xapic: 12313907508.50 ns > avic1_xapic: 19106424733.30 ns > avic0_x2apic: 13073988486.00 ns I think it depends on the microarchitecture implementation of AVIC? Paolo
