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| author | Wanpeng Li <wanpengli@tencent.com> | 2021-05-18 15:00:32 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-05-27 14:45:52 +0300 |
| commit | 72b268a8e9307a1757f61af080e990b5baa11d2a (patch) | |
| tree | 3582e649e3f5d8da5f0fc99955a90407f903d609 | |
| parent | 6bd5b743686243dae7351d5dcceeb7f171201bb4 (diff) | |
| download | linux-72b268a8e9307a1757f61af080e990b5baa11d2a.tar.xz | |
KVM: X86: Bail out of direct yield in case of under-committed scenarios
In case of under-committed scenarios, vCPUs can be scheduled easily;
kvm_vcpu_yield_to adds extra overhead, and it is also common to see
when vcpu->ready is true but yield later failing due to p->state is
TASK_RUNNING.
Let's bail out in such scenarios by checking the length of current cpu
runqueue, which can be treated as a hint of under-committed instead of
guarantee of accuracy. 30%+ of directed-yield attempts can now avoid
the expensive lookups in kvm_sched_yield() in an under-committed scenario.
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1621339235-11131-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9b6bca616929..dfb7c320581f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8360,6 +8360,9 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id) vcpu->stat.directed_yield_attempted++; + if (single_task_running()) + goto no_yield; + rcu_read_lock(); map = rcu_dereference(vcpu->kvm->arch.apic_map); |