Hi all, 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 ebizzy -M (Destination Shorthand is All excluding self) avic0_xapic 9416 records/s real 10.00 s user 4.80 s sys 1693.25 s avic1_xapic 18157 records/s real 10.00 s user 10.69 s sys 1779.80 s avic0_x2apic 74507 records/s real 10.00 s user 48.98 s sys 1752.12 s ./hackbench -l 1000000 (Destination Shorthand is Destination) avic0_xapic Time: 121.339 avic1_xapic Time: 117.840 avic0_x2apic Time: 118.753 Any thoughts? Wanpeng
