This moves the equivalence cache implementation out of the 'core'
package and into k8s.io/kubernetes/pkg/scheduler/core/equivalence.
Separating the equiv. cache from the genericScheduler implementation
make their interaction points easier to follow, and prevents us from
accidentally accessing unexported fields.
Automatic merge from submit-queue (batch tested with PRs 64142, 64426, 62910, 63942, 64548). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
scheduler: further cleanup of equivalence cache
**What this PR does / why we need it**:
This improves comments and simplifies some names/logic in equivalence_cache.go, as well as changing the order of some items in the file.
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
/kind cleanup
Part of https://github.com/kubernetes/kubernetes/pull/63040 is the
assumption that scheduler cache updates must happen before equivalence
cache updates for any given informer event.
The reason for this is that the equivalence cache implementation checks
the main cache for staleness while holding the equiv. cache write lock.
case 1: If an informer invalidates an equiv. cache entry before the
staleness check, then we know that the main cache update completed.
case 2: If an informer blocks trying to grab the equiv. cache lock, then
invalidation will occur right after the potentially stale update is
written.
This patch adds a note to places where we invalidate the equivalence
cache so that hopefully nobody violates this invariant.
Automatic merge from submit-queue (batch tested with PRs 59592, 62308, 62523, 62635, 62243). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Separate pod priority from preemption
**What this PR does / why we need it**:
Users request to split priority and preemption feature gate so they can use priority separately.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#62068
**Special notes for your reviewer**:
~~I kept use `ENABLE_POD_PRIORITY` as ENV name for gce cluster scripts for backward compatibility reason. Please let me know if other approach is preffered.~~
~~This is a potential **break change** as existing clusters will be affected, we may need to include this in 1.11 maybe?~~
TODO: update this doc https://kubernetes.io/docs/concepts/configuration/pod-priority-preemption/
[Update] Usage: in config file for scheduler:
```yaml
apiVersion: componentconfig/v1alpha1
kind: KubeSchedulerConfiguration
...
disablePreemption: true
```
**Release note**:
```release-note
Split PodPriority and PodPreemption feature gate
```
This moves plugin/pkg/scheduler to pkg/scheduler and
plugin/cmd/kube-scheduler to cmd/kube-scheduler.
Bulk of the work was done with gomvpkg, except for kube-scheduler main
package.
Avesh Agarwal