Messages in this thread | | | Date | Mon, 10 Jun 2019 16:17:17 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH v3 2/3] KVM: X86: Implement PV sched yield hypercall |
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2019-05-30 09:05+0800, Wanpeng Li: > From: Wanpeng Li <wanpengli@tencent.com> > > The target vCPUs are in runnable state after vcpu_kick and suitable > as a yield target. This patch implements the sched yield hypercall. > > 17% performance increasement of ebizzy benchmark can be observed in an > over-subscribe environment. (w/ kvm-pv-tlb disabled, testing TLB flush > call-function IPI-many since call-function is not easy to be trigged > by userspace workload). > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: Liran Alon <liran.alon@oracle.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > @@ -7172,6 +7172,28 @@ void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu) > kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu); > } > > +static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id) > +{ > + struct kvm_vcpu *target = NULL; > + struct kvm_apic_map *map = NULL; > + > + rcu_read_lock(); > + map = rcu_dereference(kvm->arch.apic_map); > + > + if (unlikely(!map) || dest_id > map->max_apic_id) > + goto out; > + > + if (map->phys_map[dest_id]->vcpu) {
This should check for map->phys_map[dest_id].
> + target = map->phys_map[dest_id]->vcpu; > + rcu_read_unlock(); > + kvm_vcpu_yield_to(target); > + } > + > +out: > + if (!target) > + rcu_read_unlock();
Also, I find the following logic clearer
{ struct kvm_vcpu *target = NULL; struct kvm_apic_map *map; rcu_read_lock(); map = rcu_dereference(kvm->arch.apic_map); if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id]) target = map->phys_map[dest_id]->vcpu; rcu_read_unlock(); if (target) kvm_vcpu_yield_to(target); }
thanks.
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