On 09/24/2012 09:16 AM, Gleb Natapov wrote: > 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); > } >
Even better would be not to account heavyweight exits as steal time. But we'd need a sched_exit preempt notifier for that. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
