perf: Prevent wasted time on adding to LRU cache during large commits

cache/cache.go

@@ -32,6 +32,9 @@ type Cache interface {
 
 	// Len returns the cache length.
 	Len() int
+
+	// Capacity returns the maximum number of nodes the cache can hold.
+	Capacity() int
 }
 
 // lruCache is an LRU cache implementation.
@@ -96,6 +99,10 @@ func (c *lruCache) Len() int {
 	return c.ll.Len()
 }
 
+func (c *lruCache) Capacity() int {
+	return c.maxElementCount
+}
+
 func (c *lruCache) Remove(key []byte) Node {
 	if elem, exists := c.dict[string(key)]; exists {
 		return c.removeWithKey(elem, string(key))

mutable_tree.go

@@ -745,7 +745,7 @@ func (tree *MutableTree) SaveVersion() ([]byte, int64, error) {
 				// it will update the legacy node to the new format
 				// which ensures the reference node is not a legacy node
 				tree.root.isLegacy = false
-				if err := tree.ndb.SaveNode(tree.root); err != nil {
+				if err := tree.ndb.SaveNode(tree.root, true); err != nil {
 					return nil, 0, fmt.Errorf("failed to save the reference legacy node: %w", err)
 				}
 			}
@@ -1044,8 +1044,11 @@ func (tree *MutableTree) saveNewNodes(version int64) error {
 		return err
 	}
 
-	for _, node := range newNodes {
-		if err := tree.ndb.SaveNode(node); err != nil {
+	cacheCapacity := tree.ndb.nodeCache.Capacity()
+	for i, node := range newNodes {
+		// only add up to cacheCapacity nodes to the cache
+		addToLruCache := i < cacheCapacity
+		if err := tree.ndb.SaveNode(node, addToLruCache); err != nil {
 			return err
 		}
 		node.leftNode, node.rightNode = nil, nil

nodedb.go

@@ -204,7 +204,7 @@ func (ndb *nodeDB) GetFastNode(key []byte) (*fastnode.Node, error) {
 }
 
 // SaveNode saves a node to disk.
-func (ndb *nodeDB) SaveNode(node *Node) error {
+func (ndb *nodeDB) SaveNode(node *Node, useLruCache bool) error {
 	ndb.mtx.Lock()
 	defer ndb.mtx.Unlock()
 
@@ -225,7 +225,9 @@ func (ndb *nodeDB) SaveNode(node *Node) error {
 	}
 
 	ndb.logger.Debug("BATCH SAVE", "node", node)
-	ndb.nodeCache.Add(node)
+	if useLruCache {
+		ndb.nodeCache.Add(node)
+	}
 	return nil
 }
 
@@ -386,7 +388,7 @@ func (ndb *nodeDB) deleteVersion(version int64) error {
 		}
 		// instead, the root should be reformatted to (version, 0)
 		root.nodeKey.nonce = 0
-		if err := ndb.SaveNode(root); err != nil {
+		if err := ndb.SaveNode(root, true); err != nil {
 			return err
 		}
 	}

tree_test.go

@@ -1775,7 +1775,7 @@ func TestNodeCacheStatisic(t *testing.T) {
 		expectCacheMissCnt     int
 	}{
 		"with_cache": {
-			cacheSize:              numKeyVals,
+			cacheSize:              2 * numKeyVals, // has to cover all inner nodes
 			expectFastCacheHitCnt:  numKeyVals,
 			expectFastCacheMissCnt: 0,
 			expectCacheHitCnt:      1,