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KVM: X86: Count attempted/successful directed yield

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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: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1617941911-5338-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li 2021-04-09 12:18:30 +08:00 committed by Paolo Bonzini
parent 2b519b5797
commit 4a7132efff
2 changed files with 20 additions and 6 deletions
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2
arch/x86/include/asm/kvm_host.h
View File

@ -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;

24
arch/x86/kvm/x86.c
View File

@ -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: