Merge pull request #66862 from resouer/sync-map

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
```

pkg/scheduler/core/equivalence/eqivalence.go

@@ -35,9 +35,6 @@ import (
 	"github.com/golang/glog"
 )
 
-// nodeMap stores a *Cache for each node.
-type nodeMap map[string]*NodeCache
-
 // Cache is a thread safe map saves and reuses the output of predicate functions,
 // it uses node name as key to access those cached results.
 //
@@ -45,17 +42,13 @@ type nodeMap map[string]*NodeCache
 // class". (Equivalence class is defined in the `Class` type.) Saved results
 // will be reused until an appropriate invalidation function is called.
 type Cache struct {
-	// NOTE(harry): Theoretically sync.Map has better performance in machine with 8+ CPUs, while
-	// the reality is lock contention in first level cache is rare.
-	mu          sync.RWMutex
-	nodeToCache nodeMap
+	// i.e. map[string]*NodeCache
+	sync.Map
 }
 
 // NewCache create an empty equiv class cache.
 func NewCache() *Cache {
-	return &Cache{
-		nodeToCache: make(nodeMap),
-	}
+	return new(Cache)
 }
 
 // NodeCache saves and reuses the output of predicate functions. Use RunPredicate to
@@ -83,12 +76,8 @@ func newNodeCache() *NodeCache {
 // it creates the NodeCache and returns it.
 // The boolean flag is true if the value was loaded, false if created.
 func (c *Cache) GetNodeCache(name string) (nodeCache *NodeCache, exists bool) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-	if nodeCache, exists = c.nodeToCache[name]; !exists {
-		nodeCache = newNodeCache()
-		c.nodeToCache[name] = nodeCache
-	}
+	v, exists := c.LoadOrStore(name, newNodeCache())
+	nodeCache = v.(*NodeCache)
 	return
 }
 
@@ -97,12 +86,13 @@ func (c *Cache) InvalidatePredicates(predicateKeys sets.String) {
 	if len(predicateKeys) == 0 {
 		return
 	}
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-	for _, n := range c.nodeToCache {
+	c.Range(func(k, v interface{}) bool {
+		n := v.(*NodeCache)
 		n.invalidatePreds(predicateKeys)
-	}
+		return true
+	})
 	glog.V(5).Infof("Cache invalidation: node=*,predicates=%v", predicateKeys)
+
 }
 
 // InvalidatePredicatesOnNode clears cached results for the given predicates on one node.
@@ -110,9 +100,8 @@ func (c *Cache) InvalidatePredicatesOnNode(nodeName string, predicateKeys sets.S
 	if len(predicateKeys) == 0 {
 		return
 	}
-	c.mu.RLock()
-	defer c.mu.RUnlock()
-	if n, ok := c.nodeToCache[nodeName]; ok {
+	if v, ok := c.Load(nodeName); ok {
+		n := v.(*NodeCache)
 		n.invalidatePreds(predicateKeys)
 	}
 	glog.V(5).Infof("Cache invalidation: node=%s,predicates=%v", nodeName, predicateKeys)
@@ -120,9 +109,7 @@ func (c *Cache) InvalidatePredicatesOnNode(nodeName string, predicateKeys sets.S
 
 // InvalidateAllPredicatesOnNode clears all cached results for one node.
 func (c *Cache) InvalidateAllPredicatesOnNode(nodeName string) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-	delete(c.nodeToCache, nodeName)
+	c.Delete(nodeName)
 	glog.V(5).Infof("Cache invalidation: node=%s,predicates=*", nodeName)
 }
 

pkg/scheduler/core/equivalence/eqivalence_test.go

@@ -731,7 +731,7 @@ func TestInvalidateCachedPredicateItemOfAllNodes(t *testing.T) {
 	// there should be no cached predicate any more
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			if nodeCache, exist := ecache.nodeToCache[test.nodeName]; exist {
+			if nodeCache, exist := ecache.GetNodeCache(test.nodeName); exist {
 				if _, exist := nodeCache.cache[testPredicate]; exist {
 					t.Errorf("Failed: cached item for predicate key: %v on node: %v should be invalidated",
 						testPredicate, test.nodeName)