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| author | Wanpeng Li <wanpengli@tencent.com> | 2020-09-10 17:50:41 +0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-09-28 07:57:10 -0400 |
| commit | 010fd37fddf659ea7525b1191381e6f8c3ccab14 (patch) | |
| tree | fb912e929c3e402bbd3e73ff706b6b616e4b6d5d /arch/x86/kvm/vmx/vmx.c | |
| parent | 68ca7663c75b099539fe675fc5387dee44d3a6cc (diff) | |
| download | lwn-010fd37fddf659ea7525b1191381e6f8c3ccab14.tar.gz lwn-010fd37fddf659ea7525b1191381e6f8c3ccab14.zip | |
KVM: LAPIC: Reduce world switch latency caused by timer_advance_ns
All the checks in lapic_timer_int_injected(), __kvm_wait_lapic_expire(), and
these function calls waste cpu cycles when the timer mode is not tscdeadline.
We can observe ~1.3% world switch time overhead by kvm-unit-tests/vmexit.flat
vmcall testing on AMD server. This patch reduces the world switch latency
caused by timer_advance_ns feature when the timer mode is not tscdeadline by
simpling move the check against apic->lapic_timer.expired_tscdeadline much
earlier.
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1599731444-3525-7-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index d4dfb7a23a0c..f4cfc18366de 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6800,9 +6800,7 @@ reenter_guest: if (enable_preemption_timer) vmx_update_hv_timer(vcpu); - if (lapic_in_kernel(vcpu) && - vcpu->arch.apic->lapic_timer.timer_advance_ns) - kvm_wait_lapic_expire(vcpu); + kvm_wait_lapic_expire(vcpu); /* * If this vCPU has touched SPEC_CTRL, restore the guest's value if |