[v2,05/43] KVM: Update halt-polling stats if and only if halt-polling was attempted

Commit Message

Sean Christopherson Oct. 9, 2021, 2:11 a.m. UTC

Don't update halt-polling stats if halt-polling wasn't attempted.  This
is a nop as @poll_ns is guaranteed to be '0' (poll_end == start), but it
will allow a future patch to move the histogram stats into the helper to
resolve a discrepancy in what is considered a "successful" halt-poll.

No functional change intended.

Reviewed-by: David Matlack <[e-mail]>
Signed-off-by: Sean Christopherson <[e-mail]>
---
 virt/kvm/kvm_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

Maxim Levitsky Oct. 27, 2021, 10:18 a.m. UTC | #1

On Fri, 2021-10-08 at 19:11 -0700, Sean Christopherson wrote:
> Don't update halt-polling stats if halt-polling wasn't attempted.  This
> is a nop as @poll_ns is guaranteed to be '0' (poll_end == start), but it
> will allow a future patch to move the histogram stats into the helper to
> resolve a discrepancy in what is considered a "successful" halt-poll.
> 
> No functional change intended.
> 
> Reviewed-by: David Matlack <[e-mail]>
> Signed-off-by: Sean Christopherson <[e-mail]>
> ---
>  virt/kvm/kvm_main.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 5d4a90032277..6156719bcbbc 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3217,6 +3217,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  {
>  	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
>  	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
> +	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
>  	ktime_t start, cur, poll_end;
>  	bool waited = false;
>  	u64 block_ns;
> @@ -3224,7 +3225,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  	kvm_arch_vcpu_blocking(vcpu);
>  
>  	start = cur = poll_end = ktime_get();
> -	if (vcpu->halt_poll_ns && halt_poll_allowed) {
> +	if (do_halt_poll) {
>  		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
>  
>  		++vcpu->stat.generic.halt_attempted_poll;
> @@ -3276,8 +3277,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  	kvm_arch_vcpu_unblocking(vcpu);
>  	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
>  
> -	update_halt_poll_stats(
> -		vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
> +	if (do_halt_poll)
> +		update_halt_poll_stats(
> +			vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
>  
>  	if (halt_poll_allowed) {
>  		if (!vcpu_valid_wakeup(vcpu)) {
Reviewed-by: Maxim Levitsky <[e-mail]>

Best regards,
	Maxim Levitsky

Patch

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5d4a90032277..6156719bcbbc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3217,6 +3217,7 @@  void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 {
 	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
 	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
+	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
 	ktime_t start, cur, poll_end;
 	bool waited = false;
 	u64 block_ns;
@@ -3224,7 +3225,7 @@  void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_blocking(vcpu);
 
 	start = cur = poll_end = ktime_get();
-	if (vcpu->halt_poll_ns && halt_poll_allowed) {
+	if (do_halt_poll) {
 		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
 
 		++vcpu->stat.generic.halt_attempted_poll;
@@ -3276,8 +3277,9 @@  void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_unblocking(vcpu);
 	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
-	update_halt_poll_stats(
-		vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
+	if (do_halt_poll)
+		update_halt_poll_stats(
+			vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
 
 	if (halt_poll_allowed) {
 		if (!vcpu_valid_wakeup(vcpu)) {