ping, On Fri, 1 Apr 2022 at 16:10, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: > > The missing semantic gap that occurs when a guest OS is preempted > when executing its own critical section, this leads to degradation > of application scalability. We try to bridge this semantic gap in > some ways, by passing guest preempt_count to the host and checking > guest irq disable state, the hypervisor now knows whether guest > OSes are running in the critical section, the hypervisor yield-on-spin > heuristics can be more smart this time to boost the vCPU candidate > who is in the critical section to mitigate this preemption problem, > in addition, it is more likely to be a potential lock holder. > > Testing on 96 HT 2 socket Xeon CLX server, with 96 vCPUs VM 100GB RAM, > one VM running benchmark, the other(none-2) VMs running cpu-bound > workloads, There is no performance regression for other benchmarks > like Unixbench etc. > > 1VM > vanilla optimized improved > > hackbench -l 50000 > 28 21.45 30.5% > ebizzy -M > 12189 12354 1.4% > dbench > 712 MB/sec 722 MB/sec 1.4% > > 2VM: > vanilla optimized improved > > hackbench -l 10000 > 29.4 26 13% > ebizzy -M > 3834 4033 5% > dbench > 42.3 MB/sec 44.1 MB/sec 4.3% > > 3VM: > vanilla optimized improved > > hackbench -l 10000 > 47 35.46 33% > ebizzy -M > 3828 4031 5% > dbench > 30.5 MB/sec 31.16 MB/sec 2.3% > > v1 -> v2: > * add more comments to irq disable state > * renaming irq_disabled to last_guest_irq_disabled > * renaming, inverting the return, and also return a bool for kvm_vcpu_non_preemptable > > Wanpeng Li (5): > KVM: X86: Add MSR_KVM_PREEMPT_COUNT support > KVM: X86: Add last guest interrupt disable state support > KVM: X86: Boost vCPU which is in critical section > x86/kvm: Add MSR_KVM_PREEMPT_COUNT guest support > KVM: X86: Expose PREEMT_COUNT CPUID feature bit to guest > > Documentation/virt/kvm/cpuid.rst | 3 ++ > arch/x86/include/asm/kvm_host.h | 8 ++++ > arch/x86/include/uapi/asm/kvm_para.h | 2 + > arch/x86/kernel/kvm.c | 10 +++++ > arch/x86/kvm/cpuid.c | 3 +- > arch/x86/kvm/x86.c | 60 ++++++++++++++++++++++++++++ > include/linux/kvm_host.h | 1 + > virt/kvm/kvm_main.c | 7 ++++ > 8 files changed, 93 insertions(+), 1 deletion(-) > > -- > 2.25.1 >
