diff --git a/pkg/apis/core/helper/qos/qos.go b/pkg/apis/core/helper/qos/qos.go
index 6323122f98c..b32fffa0e3f 100644
--- a/pkg/apis/core/helper/qos/qos.go
+++ b/pkg/apis/core/helper/qos/qos.go
@@ -39,7 +39,8 @@ func GetPodQOS(pod *core.Pod) core.PodQOSClass {
 	return ComputePodQOS(pod)
 }
 
-// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is expensive.
+// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is more
+// expensive than GetPodQOS which should be used for pods having a non-empty .Status.QOSClass.
 // A pod is besteffort if none of its containers have specified any requests or limits.
 // A pod is guaranteed only when requests and limits are specified for all the containers and they are equal.
 // A pod is burstable if limits and requests do not match across all containers.
diff --git a/pkg/apis/core/v1/helper/qos/qos.go b/pkg/apis/core/v1/helper/qos/qos.go
index e0db483dcca..79e2eb2abd2 100644
--- a/pkg/apis/core/v1/helper/qos/qos.go
+++ b/pkg/apis/core/v1/helper/qos/qos.go
@@ -41,7 +41,8 @@ func GetPodQOS(pod *v1.Pod) v1.PodQOSClass {
 	return ComputePodQOS(pod)
 }
 
-// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is expensive.
+// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is more
+// expensive than GetPodQOS which should be used for pods having a non-empty .Status.QOSClass.
 // A pod is besteffort if none of its containers have specified any requests or limits.
 // A pod is guaranteed only when requests and limits are specified for all the containers and they are equal.
 // A pod is burstable if limits and requests do not match across all containers.
diff --git a/staging/src/k8s.io/kubectl/pkg/util/qos/qos.go b/staging/src/k8s.io/kubectl/pkg/util/qos/qos.go
index 16a8846a799..68b1b9072a9 100644
--- a/staging/src/k8s.io/kubectl/pkg/util/qos/qos.go
+++ b/staging/src/k8s.io/kubectl/pkg/util/qos/qos.go
@@ -37,7 +37,8 @@ func GetPodQOS(pod *core.Pod) core.PodQOSClass {
 	return ComputePodQOS(pod)
 }
 
-// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is expensive.
+// ComputePodQOS evaluates the list of containers to determine a pod's QoS class. This function is more
+// expensive than GetPodQOS which should be used for pods having a non-empty .Status.QOSClass.
 // A pod is besteffort if none of its containers have specified any requests or limits.
 // A pod is guaranteed only when requests and limits are specified for all the containers and they are equal.
 // A pod is burstable if limits and requests do not match across all containers.