| Message ID | CANRm+Cz6Es1TLFdGxz_65i-4osE6=67J=noqWC6n09TeXSJ5SA@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/2] KVM: X86: Less kvmclock sync induced vmexits after VM boots | expand |
On Mon, 17 Feb 2020 at 18:36, Wanpeng Li <kernellwp@gmail.com> wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > In the progress of vCPUs creation, it queues a kvmclock sync worker to > the global > workqueue before each vCPU creation completes. Each worker will be scheduled > after 300 * HZ delay and request a kvmclock update for all vCPUs and kick them > out. This is especially worse when scaling to large VMs due to a lot of vmexits. > Just one worker as a leader to trigger the kvmclock sync request for > all vCPUs is > enough. Sorry for the alignment. > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/kvm/x86.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index fb5d64e..d0ba2d4 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) > if (!kvmclock_periodic_sync) > return; > > - schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > - KVMCLOCK_SYNC_PERIOD); > + if (kvm->created_vcpus == 1) > + schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > + KVMCLOCK_SYNC_PERIOD); > } > > void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) > -- > 2.7.4
On 17/02/20 11:36, Wanpeng Li wrote: > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index fb5d64e..d0ba2d4 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) > if (!kvmclock_periodic_sync) > return; > > - schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > - KVMCLOCK_SYNC_PERIOD); > + if (kvm->created_vcpus == 1) > + schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > + KVMCLOCK_SYNC_PERIOD); This is called with kvm->lock not held, so you can have kvm->created_vcpus == 2 by the time you get here. You can test instead "if (vcpu->vcpu_idx == 0)". Thanks, Paolo
On Mon, 17 Feb 2020 at 19:23, Paolo Bonzini <pbonzini@redhat.com> wrote: > > On 17/02/20 11:36, Wanpeng Li wrote: > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index fb5d64e..d0ba2d4 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) > > if (!kvmclock_periodic_sync) > > return; > > > > - schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > > - KVMCLOCK_SYNC_PERIOD); > > + if (kvm->created_vcpus == 1) > > + schedule_delayed_work(&kvm->arch.kvmclock_sync_work, > > + KVMCLOCK_SYNC_PERIOD); > > This is called with kvm->lock not held, so you can have > kvm->created_vcpus == 2 by the time you get here. You can test instead > "if (vcpu->vcpu_idx == 0)". Agreed. Wanpeng
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fb5d64e..d0ba2d4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) if (!kvmclock_periodic_sync) return; - schedule_delayed_work(&kvm->arch.kvmclock_sync_work, - KVMCLOCK_SYNC_PERIOD); + if (kvm->created_vcpus == 1) + schedule_delayed_work(&kvm->arch.kvmclock_sync_work, + KVMCLOCK_SYNC_PERIOD); } void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)