2017-11-10 15:04 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>: > Remote flushing api's does a busy wait which is fine in bare-metal > scenario. But with-in the guest, the vcpus might have been pre-empted > or blocked. In this scenario, the initator vcpu would end up > busy-waiting for a long amount of time. > > This patch set implements para-virt flush tlbs making sure that it > does not wait for vcpus that are sleeping. And all the sleeping vcpus > flush the tlb on guest enter. Idea was discussed here: > https://lkml.org/lkml/2012/2/20/157 > > The best result is achieved when we're overcommiting the host by running > multiple vCPUs on each pCPU. In this case PV tlb flush avoids touching > vCPUs which are not scheduled and avoid the wait on the main CPU. > > In addition, thanks for commit 9e52fc2b50d ("x86/mm: Enable RCU based > page table freeing (CONFIG_HAVE_RCU_TABLE_FREE=y)") > > Test on a Haswell i7 desktop 4 cores (2HT), so 8 pCPUs, running ebizzy in > one linux guest. > > ebizzy -M > vanilla optimized boost > 8 vCPUs 10152 10083 -0.68% > 16 vCPUs 1224 4866 297.5% > 24 vCPUs 1109 3871 249% > 32 vCPUs 1025 3375 229.3% v1 -> v2: * a new CPUID feature bit * fix cmpxchg check * use kvm_vcpu_flush_tlb() to get the statistics right * just OR the KVM_VCPU_PREEMPTED in kvm_steal_time_set_preempted * add a new bool argument to kvm_x86_ops->tlb_flush * __cpumask_clear_cpu() instead of cpumask_clear_cpu() * not put cpumask_t on stack * rebase the patchset against "locking/qspinlock/x86: Avoid test-and-set when PV_DEDICATED is set" v3 > > Wanpeng Li (4): > KVM: Add vCPU running/preempted state > KVM: Add paravirt remote TLB flush > KVM: X86: introduce invalidate_gpa argument to tlb flush > KVM: Add flush_on_enter before guest enter > > Documentation/virtual/kvm/cpuid.txt | 10 ++++++++++ > arch/x86/include/asm/kvm_host.h | 2 +- > arch/x86/include/uapi/asm/kvm_para.h | 6 ++++++ > arch/x86/kernel/kvm.c | 35 ++++++++++++++++++++++++++++++++++- > arch/x86/kvm/cpuid.c | 3 ++- > arch/x86/kvm/svm.c | 14 +++++++------- > arch/x86/kvm/vmx.c | 21 +++++++++++---------- > arch/x86/kvm/x86.c | 24 +++++++++++++++--------- > 8 files changed, 86 insertions(+), 29 deletions(-) > > -- > 2.7.4 >
