On Mon, Sep 24, 2012 at 03:24:47PM +0900, Takuya Yoshikawa wrote:
> This is an RFC since I have not done any comparison with the approach
> using for_each_set_bit() which can be seen in Avi's work.
>
> Takuya
> ---
>
> We did a simple test to see which requests we would get at the same time
> in vcpu_enter_guest() and got the following numbers:
>
> |...........|...............|........|...............|.|
> (N) (E) (S) (ES) others
> 22.3% 30.7% 16.0% 29.5% 1.4%
>
> (N) : Nothing
> (E) : Only KVM_REQ_EVENT
> (S) : Only KVM_REQ_STEAL_UPDATE
> (ES): Only KVM_REQ_EVENT and KVM_REQ_STEAL_UPDATE
>
> * Note that the exact numbers can change for other guests.
>
Yes, for guests that do not enable steal time KVM_REQ_STEAL_UPDATE
should be never set, but currently it is. The patch (not tested) should
fix this.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 901ad00..01572f5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1544,6 +1544,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu)
delta = current->sched_info.run_delay - vcpu->arch.st.last_steal;
vcpu->arch.st.last_steal = current->sched_info.run_delay;
vcpu->arch.st.accum_steal = delta;
+
+ kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
}
static void record_steal_time(struct kvm_vcpu *vcpu)
@@ -1673,8 +1675,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr,
u64 data)
accumulate_steal_time(vcpu);
preempt_enable();
- kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
-
break;
case MSR_KVM_PV_EOI_EN:
if (kvm_lapic_enable_pv_eoi(vcpu, data))
@@ -2336,7 +2336,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
}
accumulate_steal_time(vcpu);
- kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
--
Gleb.
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