Re: [RFC 3/7] measure time out of guest

[Zachary Amsden <zamsden@redhat.com>]

On 08/25/2010 11:43 AM, Glauber Costa wrote:
> By measuring time between a vcpu_put and a vcpu_load, we can
> estimate how much time did the guest stay out of the cpu.
> This is exported to the guest at every clock update.
>
> Signed-off-by: Glauber Costa<glommer@redhat.com>
> ---
>   arch/x86/include/asm/kvm_host.h |    2 ++
>   arch/x86/kvm/x86.c              |   12 +++++++++++-
>   2 files changed, 13 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 502e53f..bc28aff 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -364,6 +364,8 @@ struct kvm_vcpu_arch {
>   	u64 hv_vapic;
>
>   	cpumask_var_t wbinvd_dirty_mask;
> +	u64 time_out;
> +	u64 last_time_out;
>   };
>
>   struct kvm_arch {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e7e3b50..680feaa 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -925,8 +925,9 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
>   	vcpu->hv_clock.system_time = ts.tv_nsec +
>   				     (NSEC_PER_SEC * (u64)ts.tv_sec) + v->kvm->arch.kvmclock_offset;
>
> -	vcpu->hv_clock.flags = 0;
> +	vcpu->hv_clock.flags = PVCLOCK_STEAL_BIT;
>
> +	vcpu->hv_clock.steal_time = vcpu->time_out / 1000000;
>   	/*
>   	 * The interface expects us to write an even number signaling that the
>   	 * update is finished. Since the guest won't see the intermediate
> @@ -1798,6 +1799,8 @@ static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)
>
>   void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   {
> +	s64 now;
> +
>   	/* Address WBINVD may be executed by guest */
>   	if (need_emulate_wbinvd(vcpu)) {
>   		if (kvm_x86_ops->has_wbinvd_exit())
> @@ -1815,12 +1818,19 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   		per_cpu(cpu_tsc_khz, cpu) = khz;
>   	}
>   	kvm_request_guest_time_update(vcpu);
> +
> +	now = getnsboottime();
> +
> +	if (vcpu->arch.last_time_out != 0)
> +		vcpu->arch.time_out += now - vcpu->arch.last_time_out;
>    


>   }
>
>   void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>   {
>   	kvm_x86_ops->vcpu_put(vcpu);
>   	kvm_put_guest_fpu(vcpu);
> +
> +	vcpu->arch.last_time_out = getnsboottime();
>   }
>
>   static int is_efer_nx(void)
>    

I think I've added some of the same instrumentation in my series.