Commit 4a7132ef authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
Browse files

KVM: X86: Count attempted/successful directed yield 



To analyze some performance issues with lock contention and scheduling,
it is nice to know when directed yield are successful or failing.

Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Message-Id: <1617941911-5338-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2b519b57

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -1146,6 +1146,8 @@ struct kvm_vcpu_stat { 
	u64 halt_poll_success_ns;

	u64 halt_poll_fail_ns;

	u64 nested_run;

	u64 directed_yield_attempted;

	u64 directed_yield_successful;

};



struct x86_instruction_info;

arch/x86/kvm/x86.c

+18 −6
Original line number Diff line number Diff line
@@ -246,6 +246,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { 
	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),

	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),

	VCPU_STAT("nested_run", nested_run),

	VCPU_STAT("directed_yield_attempted", directed_yield_attempted),

	VCPU_STAT("directed_yield_successful", directed_yield_successful),

	VM_STAT("mmu_shadow_zapped", mmu_shadow_zapped),

	VM_STAT("mmu_pte_write", mmu_pte_write),

	VM_STAT("mmu_pde_zapped", mmu_pde_zapped),
@@ -8208,21 +8210,31 @@ void kvm_apicv_init(struct kvm *kvm, bool enable) 
}

EXPORT_SYMBOL_GPL(kvm_apicv_init);



static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)

static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)

{

	struct kvm_vcpu *target = NULL;

	struct kvm_apic_map *map;



	vcpu->stat.directed_yield_attempted++;



	rcu_read_lock();

	map = rcu_dereference(kvm->arch.apic_map);

	map = rcu_dereference(vcpu->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 && READ_ONCE(target->ready))

		kvm_vcpu_yield_to(target);

	if (!target || !READ_ONCE(target->ready))

		goto no_yield;



	if (kvm_vcpu_yield_to(target) <= 0)

		goto no_yield;



	vcpu->stat.directed_yield_successful++;



no_yield:

	return;

}



int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
@@ -8269,7 +8281,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) 
			break;



		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);

		kvm_sched_yield(vcpu->kvm, a1);

		kvm_sched_yield(vcpu, a1);

		ret = 0;

		break;

#ifdef CONFIG_X86_64
@@ -8287,7 +8299,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) 
		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SCHED_YIELD))

			break;



		kvm_sched_yield(vcpu->kvm, a0);

		kvm_sched_yield(vcpu, a0);

		ret = 0;

		break;

	default: