- Images for cloud-controller-manager, kube-apiserver, kube-controller-manager, and kube-scheduler now contain a minimal /etc/nsswitch.conf and should respect /etc/hosts for lookups ([#69238](https://github.com/kubernetes/kubernetes/pull/69238), [@BenTheElder](https://github.com/BenTheElder))

### SIG Scheduling

- Changed Job controller to use the controller UID index for Pod lookups to improve performance. ([#132305](https://github.com/kubernetes/kubernetes/pull/132305), [@xigang](https://github.com/xigang))

- Hostnames are now converted to lowercase before being used for node lookups in the kubernetes-worker charm. ([#65487](https://github.com/kubernetes/kubernetes/pull/65487), [@dshcherb](https://github.com/dshcherb))

* The following deprecated flags were removed from `kube-controller-manager`:

  * `replication-controller-lookup-cache-size`
  * `replicaset-lookup-cache-size`
  * `daemonset-lookup-cache-size`

  Don't use these flags. Using deprecated flags causes the server to print a warning. Using a removed flag causes the server to abort the startup.

- Fix performance regression in scheduler caused by frequent metric lookup on critical code path. ([#117617](https://github.com/kubernetes/kubernetes/pull/117617), [@tosi3k](https://github.com/tosi3k)) [SIG Scheduling]

* kubelet: resolved hang/timeout issues when running large numbers of pods with unique configmap/secret references by reverting to 1.11 configmap/secret lookup behavior ([#74755](https://github.com/kubernetes/kubernetes/pull/74755), [@liggitt](https://github.com/liggitt))

resources, which represents the list of group aliases (e.g. "all") that every resource belongs to. ([#43338](https://github.com/kubernetes/kubernetes/pull/43338), [@fabianofranz](https://github.com/fabianofranz))

* `--service-account-lookup` now defaults to true, requiring the Secret API object containing the token to exist in order for a service account token to be valid. This enables service account tokens to be revoked by deleting the Secret object containing the token. ([#44071]...

- Fixed performance regression in scheduler caused by frequent metric lookup on critical code path. ([#117594](https://github.com/kubernetes/kubernetes/pull/117594), [@tosi3k](https://github.com/tosi3k))

- Fixed an issue that could cause the kubelet to incorrectly run concurrent pod reconciliation loops and crash. ([#89055](https://github.com/kubernetes/kubernetes/pull/89055), [@tedyu](https://github.com/tedyu)) [SIG Node]

- `client-go`, using log level 9, traces the following events of a HTTP request:
      - DNS lookup
      - TCP dialing
      - TLS handshake
      - Time to get a connection from the pool