## Before Upgrading

Consider the following changes, limitations, and guidelines before you upgrade:

* The kubelet now fails if swap is enabled on a node. To override the default and run with /proc/swaps on, set `--fail-swap-on=false`. The experimental flag `--experimental-fail-swap-on` is deprecated in this release, and will be removed in a future release.

### Kubernetes Node system swap support

Every system administrator or Kubernetes user has been in the same boat regarding setting up and using Kubernetes: disable swap space. With the release of Kubernetes 1.22, *alpha* support is available to run nodes with swap memory. This change lets administrators opt in to configuring swap on Linux nodes, treating a portion of block storage as additional virtual memory.

Other memory operations are <i>write-like</i>, including write, atomic write, mutex unlock, channel send, and channel close.
Some, such as atomic compare-and-swap, are both read-like and write-like.
</p>

<p>
A <i>goroutine execution</i> is modeled as a set of memory operations executed by a single goroutine.
</p>

<p>
<b>Requirement 1</b>:

- Changed Linux swap handling to restrict access to swap for containers in high priority Pods.
  New Pods that have a node- or cluster-critical priority are prohibited from accessing swap on Linux,

			// was AX:DX, for which the new syntax is DX, AX. Note the reordering.
			if tok == '\n' || tok == ';' || (nesting == 0 && (tok == ',' || tok == ':')) {
				if tok == ':' {
					// Remember this location so we can swap the operands below.
					if colon >= 0 {
						p.errorf("invalid ':' in operand")
						return word, cond, operands, true
					}
					colon = len(operands)
				}
				break
			}

//		g.Offset = int64($4);
//		outcode($1, $2, &g, 0, &$7);
//	}
	MOVM	[R2,R5,R8,g], 0(R1) // MOVM	[R2,R5,R8,g], (R1)
	MOVM	[R2-R5], (R1) // MOVM [R2,R3,R4,R5], (R1)
	MOVM	[R2], (R1)

//
// SWAP
//
//	LTYPE9 cond reg ',' ireg ',' reg
//	{
//		outcode($1, $2, &$5, int32($3.Reg), &$7);
//	}
	STREX	R1, (R2), R3 // STREX (R2), R1, R3

//
// word
//
//	LTYPEH comma ximm
//	{

- Removed general available feature-gate `PDBUnhealthyPodEvictionPolicy`. ([#129500](https://github.com/kubernetes/kubernetes/pull/129500), [@carlory](https://github.com/carlory)) [SIG API Machinery, Apps and Auth]
- Start reporting swap capacity as part of `node.status.nodeSystemInfo`. ([#129954](https://github.com/kubernetes/kubernetes/pull/129954), [@iholder101](https://github.com/iholder101)) [SIG API Machinery, Apps and Node]

- Kubeadm: switch the preflight check (called 'Swap') that verifies if swap is enabled on Linux hosts to report a warning instead of an error. This is related to the graduation of the NodeSwap feature gate in the kubelet to Beta and being enabled by default in 1.23 - allows swap support on Linux hosts. In the next release of kubeadm (1.24) the preflight check will be removed, thus we recommend that you stop using...

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  - The deprecated `--show-all` flag to `kubectl get` has been removed  ([#69255](https://github.com/kubernetes/kubernetes/pull/69255), [@Pingan2017](https://github.com/Pingan2017))

- kubelet
  - The deprecated `--experimental-fail-swap-on` flag has been removed ([#69552](https://github.com/kubernetes/kubernetes/pull/69552), [@Pingan2017](https://github.com/Pingan2017))