- snapshot equivalence cache generation numbers before snapshotting the
scheduler cache
- skip update when generation does not match live generation
- keep the node and increment its generation to invalidate it instead of
deletion
- use predicates order ID as key to improve performance
Automatic merge from submit-queue (batch tested with PRs 66862, 67618). 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>.
Use sync.map to scale equiv class cache better
**What this PR does / why we need it**:
Change the current lock in first level ecache into `sync.Map`, which is known for scaling better than `sync. Mutex ` on machines with >8 CPUs
ref: https://golang.org/pkg/sync/#Map
And the code is much cleaner in this way.
5k Nodes, 10k Pods benchmark with ecache enabled in 64 cores VM:
```bash
// before
BenchmarkScheduling/5000Nodes/0Pods-64 10000 17550089 ns/op
// after
BenchmarkScheduling/5000Nodes/0Pods-64 10000 16975098 ns/op
```
Comparing to current implementation, the improvement after this change is noticeable, and the test is stable in 8, 16, 64 cores VM.
**Special notes for your reviewer**:
**Release note**:
```release-note
Use sync.map to scale ecache better
```
This adds counters to equiv. cache reads & writes. Reads are labeled by
hit/miss, while writes are labeled to indicate whether the write was
discarded.
This will give us visibility into,
- hit rate of cache reads
- ratio of reads to writes
- rate of discarded writes
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.
