The RuntimeClass alpha feature enables a node to surface multiple runtime options to support a variety of workload types.  Examples include native linux containers, and “sandboxed” containers that isolate the container from the host kernel.

  
  Enabling seccomp for your workload can have a negative performance impact depending on the kernel and container runtime version in use.
  

    * Add hugepages monitoring support
    * Fix incorrect CPU usage metrics with 4.7 kernel
    * Add tmpfs monitoring support
* Support for Huge pages in empty_dir volume plugin ([#50072](https://github.com/kubernetes/kubernetes/pull/50072), [@squall0gd](https://github.com/squall0gd))
    * [Huge pages](https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt) can now be used with empty dir volume plugin.

   ([#123737](https://github.com/kubernetes/kubernetes/pull/123737), [@enj](https://github.com/enj))
- `readOnly` volumes now support recursive read-only mounts for kernel versions >= 5.12."
   ([#123180](https://github.com/kubernetes/kubernetes/pull/123180), [@AkihiroSuda](https://github.com/AkihiroSuda))
- cri-api: Implemented KEP-3857: Recursive Read-only (RRO) mounts.

  // https://access.redhat.com/documentation/en-us/red_hat_subscription_management/1/html/rhsm/uuid
  optional string systemUUID = 2;

  // Boot ID reported by the node.
  optional string bootID = 3;

  // Kernel Version reported by the node from 'uname -r' (e.g. 3.16.0-0.bpo.4-amd64).
  optional string kernelVersion = 4;

  // OS Image reported by the node from /etc/os-release (e.g. Debian GNU/Linux 7 (wheezy)).

- Add --permit-address-sharing flag to `kube-apiserver` to listen with `SO_REUSEADDR`. While allowing to listen on wildcard IPs like 0.0.0.0 and specific IPs in parallel, it avoids waiting for the kernel to release socket in `TIME_WAIT` state, and hence, considerably reducing `kube-apiserver` restart times under certain conditions. ([#93861](https://github.com/kubernetes/kubernetes/pull/93861), [@sttts](https://github.com/sttts))

	// If true the pod's hostname will be configured as the pod's FQDN, rather than the leaf name (the default).
	// In Linux containers, this means setting the FQDN in the hostname field of the kernel (the nodename field of struct utsname).
	// In Windows containers, this means setting the registry value of hostname for the registry key HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters to FQDN.

- Kubelet: a configuration file specified via `--config` is now loaded with strict deserialization,...

- Handle Windows named pipes in host mounts. ([#69484](https://github.com/kubernetes/kubernetes/pull/69484), [@ddebroy](https://github.com/ddebroy))
- Fixed inconsistency in windows kernel proxy when updating HNS policy. ([#68923](https://github.com/kubernetes/kubernetes/pull/68923), [@delulu](https://github.com/delulu))

##  External Dependencies

- kubeadm will now not fail preflight checks when running on >= 5.0 Linux kernel ([#74355](https://github.com/kubernetes/kubernetes/pull/74355), [@brb](https://github.com/brb))