enable cgroups tiers by default.

cmd/kubelet/app/options/options.go

@@ -189,7 +189,7 @@ func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.KubeletCgroups, "kubelet-cgroups", s.KubeletCgroups, "Optional absolute name of cgroups to create and run the Kubelet in.")
 	fs.StringVar(&s.SystemCgroups, "system-cgroups", s.SystemCgroups, "Optional absolute name of cgroups in which to place all non-kernel processes that are not already inside a cgroup under `/`. Empty for no container. Rolling back the flag requires a reboot. (Default: \"\").")
 
-	fs.BoolVar(&s.CgroupsPerQOS, "cgroups-per-qos", s.CgroupsPerQOS, "Enable creation of QoS cgroup hierarchy, if true top level QoS and pod cgroups are created.")
+	fs.BoolVar(&s.CgroupsPerQOS, "cgroups-per-qos", s.CgroupsPerQOS, "Enable creation of QoS cgroup hierarchy, if true top level QoS and pod cgroups are created. [default: true]")
 	fs.StringVar(&s.CgroupDriver, "cgroup-driver", s.CgroupDriver, "Driver that the kubelet uses to manipulate cgroups on the host.  Possible values: 'cgroupfs', 'systemd'")
 	fs.StringVar(&s.CgroupRoot, "cgroup-root", s.CgroupRoot, "Optional root cgroup to use for pods. This is handled by the container runtime on a best effort basis. Default: '', which means use the container runtime default.")
 	fs.StringVar(&s.ContainerRuntime, "container-runtime", s.ContainerRuntime, "The container runtime to use. Possible values: 'docker', 'rkt'. Default: 'docker'.")
@@ -265,7 +265,7 @@ func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
 	// Node Allocatable Flags
 	fs.Var(&s.SystemReserved, "system-reserved", "A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=150G) pairs that describe resources reserved for non-kubernetes components. Currently only cpu and memory are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]")
 	fs.Var(&s.KubeReserved, "kube-reserved", "A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=150G) pairs that describe resources reserved for kubernetes system components. Currently only cpu and memory are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]")
-	fs.StringSliceVar(&s.EnforceNodeAllocatable, "enforce-node-allocatable", s.EnforceNodeAllocatable, "A comma separated list of levels of node allocatable enforcement to be enforced by kubelet. Acceptible options are 'pods', 'system-reserved' & 'kube-reserved'. If the latter two options are specified, '--system-reserved-cgroup' & '--kube-reserved-cgroup' must also be set respectively. See https://github.com/kubernetes/community/blob/master/contributors/design-proposals/node-allocatable.md for more details. [default='']")
+	fs.StringSliceVar(&s.EnforceNodeAllocatable, "enforce-node-allocatable", s.EnforceNodeAllocatable, "A comma separated list of levels of node allocatable enforcement to be enforced by kubelet. Acceptible options are 'pods', 'system-reserved' & 'kube-reserved'. If the latter two options are specified, '--system-reserved-cgroup' & '--kube-reserved-cgroup' must also be set respectively. See https://github.com/kubernetes/community/blob/master/contributors/design-proposals/node-allocatable.md for more details. [default='pods']")
 	fs.StringVar(&s.SystemReservedCgroup, "system-reserved-cgroup", s.SystemReservedCgroup, "Absolute name of the top level cgroup that is used to manage non-kubernetes components for which compute resources were reserved via '--system-reserved' flag. Ex. '/system-reserved'. [default='']")
 	fs.StringVar(&s.KubeReservedCgroup, "kube-reserved-cgroup", s.KubeReservedCgroup, "Absolute name of the top level cgroup that is used to manage kubernetes components for which compute resources were reserved via '--kube-reserved' flag. Ex. '/kube-reserved'. [default='']")
 	fs.BoolVar(&s.ExperimentalNodeAllocatableIgnoreEvictionThreshold, "experimental-allocatable-ignore-eviction", s.ExperimentalNodeAllocatableIgnoreEvictionThreshold, "When set to 'true', Hard Eviction Thresholds will be ignored while calculating Node Allocatable. See https://github.com/kubernetes/community/blob/master/contributors/design-proposals/node-allocatable.md for more details. [default=false]")

pkg/apis/componentconfig/v1alpha1/defaults.go

@@ -51,8 +51,7 @@ const (
 var (
 	zeroDuration = metav1.Duration{}
 	// Refer to [Node Allocatable](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/node-allocatable.md) doc for more information.
-	// TODO: Set the default to "pods" once cgroups per qos is turned on by default.
-	defaultNodeAllocatableEnforcement = []string{}
+	defaultNodeAllocatableEnforcement = []string{"pods"}
 )
 
 func addDefaultingFuncs(scheme *kruntime.Scheme) error {
@@ -397,10 +396,7 @@ func SetDefaults_KubeletConfiguration(obj *KubeletConfiguration) {
 		obj.IPTablesDropBit = &temp
 	}
 	if obj.CgroupsPerQOS == nil {
-		// disabled pending merge of https://github.com/kubernetes/kubernetes/pull/41753
-		// as enabling the new hierarchy without setting /Burstable/cpu.shares may cause
-		// regression.
-		temp := false
+		temp := true
 		obj.CgroupsPerQOS = &temp
 	}
 	if obj.CgroupDriver == "" {