Merge pull request #108724 from sanposhiho/cycle-state

use `sync.Map` in CycleState for better performance

pkg/scheduler/framework/cycle_state.go

@@ -41,18 +41,18 @@ type StateKey string
 // StateData stored by one plugin can be read, altered, or deleted by another plugin.
 // CycleState does not provide any data protection, as all plugins are assumed to be
 // trusted.
+// Note: CycleState uses a sync.Map to back the storage. It's aimed to optimize for the "write once and read many times" scenarios.
+// It is the recommended pattern used in all in-tree plugins - plugin-specific state is written once in PreFilter/PreScore and afterwards read many times in Filter/Score.
 type CycleState struct {
-	mx      sync.RWMutex
-	storage map[StateKey]StateData
+	// storage is keyed with StateKey, and valued with StateData.
+	storage sync.Map
 	// if recordPluginMetrics is true, PluginExecutionDuration will be recorded for this cycle.
 	recordPluginMetrics bool
 }
 
 // NewCycleState initializes a new CycleState and returns its pointer.
 func NewCycleState() *CycleState {
-	return &CycleState{
-		storage: make(map[StateKey]StateData),
-	}
+	return &CycleState{}
 }
 
 // ShouldRecordPluginMetrics returns whether PluginExecutionDuration metrics should be recorded.
@@ -78,36 +78,32 @@ func (c *CycleState) Clone() *CycleState {
 		return nil
 	}
 	copy := NewCycleState()
-	for k, v := range c.storage {
-		copy.Write(k, v.Clone())
-	}
+	c.storage.Range(func(k, v interface{}) bool {
+		copy.storage.Store(k, v.(StateData).Clone())
+		return true
+	})
+
 	return copy
 }
 
 // Read retrieves data with the given "key" from CycleState. If the key is not
 // present an error is returned.
-// This function is thread safe by acquiring an internal lock first.
+// This function is thread safe by using sync.Map.
 func (c *CycleState) Read(key StateKey) (StateData, error) {
-	c.mx.RLock()
-	defer c.mx.RUnlock()
-	if v, ok := c.storage[key]; ok {
-		return v, nil
+	if v, ok := c.storage.Load(key); ok {
+		return v.(StateData), nil
 	}
 	return nil, ErrNotFound
 }
 
 // Write stores the given "val" in CycleState with the given "key".
-// This function is thread safe by acquiring an internal lock first.
+// This function is thread safe by using sync.Map.
 func (c *CycleState) Write(key StateKey, val StateData) {
-	c.mx.Lock()
-	c.storage[key] = val
-	c.mx.Unlock()
+	c.storage.Store(key, val)
 }
 
 // Delete deletes data with the given key from CycleState.
-// This function is thread safe by acquiring an internal lock first.
+// This function is thread safe by using sync.Map.
 func (c *CycleState) Delete(key StateKey) {
-	c.mx.Lock()
-	delete(c.storage, key)
-	c.mx.Unlock()
+	c.storage.Delete(key)
 }