pods := m.activePods()
	burstablePodCPURequest := int64(0)
	reuseReqs := make(v1.ResourceList, 4)
	for i := range pods {
		pod := pods[i]
		qosClass := v1qos.GetPodQOS(pod)
		if qosClass != v1.PodQOSBurstable {
			// we only care about the burstable qos tier
			continue
		}
		req := resource.PodRequests(pod, resource.PodResourcesOptions{Reuse: reuseReqs})

	return &swapConfigurationHelper{machineInfo: machineInfo}
}

func (m swapConfigurationHelper) ConfigureLimitedSwap(lcr *runtimeapi.LinuxContainerResources, pod *v1.Pod, container *v1.Container) {
	podQos := kubeapiqos.GetPodQOS(pod)
	containerDoesNotRequestMemory := container.Resources.Requests.Memory().IsZero() && container.Resources.Limits.Memory().IsZero()

	nodeOnlyHasMemoryPressureCondition := hasNodeCondition(m.nodeConditions, v1.NodeMemoryPressure) && len(m.nodeConditions) == 1
	if nodeOnlyHasMemoryPressureCondition {
		notBestEffort := v1.PodQOSBestEffort != v1qos.GetPodQOS(attrs.Pod)
		if notBestEffort {
			return lifecycle.PodAdmitResult{Admit: true}
		}

		// When node has memory pressure, check BestEffort Pod's toleration:

func (podStrategy) PrepareForCreate(ctx context.Context, obj runtime.Object) {
	pod := obj.(*api.Pod)
	pod.Status = api.PodStatus{
		Phase:    api.PodPending,
		QOSClass: qos.GetPodQOS(pod),
	}

	podutil.DropDisabledPodFields(pod, nil)

	applySchedulingGatedCondition(pod)
	mutatePodAffinity(pod)
	applyAppArmorVersionSkew(ctx, pod)
}

	}
	if len(apiPodStatus.PodIPs) > 0 {
		apiPodStatus.PodIP = apiPodStatus.PodIPs[0].IP
	}

	// set status for Pods created on versions of kube older than 1.6
	apiPodStatus.QOSClass = v1qos.GetPodQOS(pod)

	apiPodStatus.ContainerStatuses = kl.convertToAPIContainerStatuses(
		pod, podStatus,
		oldPodStatus.ContainerStatuses,
		pod.Spec.Containers,
		len(pod.Spec.InitContainers) > 0,
		false,
	)

  It reduces the number of kinds of cluster events the scheduler needs to subscribe/handle. ([#121571](https://github.com/kubernetes/kubernetes/pull/121571), [@sanposhiho](https://github.com/sanposhiho))

	// so far and save the cost of a deep copy.
	if apiequality.Semantic.DeepEqual(newPod.Spec, oldPod.Spec) {
		return allErrs
	}

	if qos.GetPodQOS(oldPod) != qos.ComputePodQOS(newPod) {
		allErrs = append(allErrs, field.Invalid(fldPath, newPod.Status.QOSClass, "Pod QoS is immutable"))
	}