Optimize radix tree matching (#364)

python/sglang/srt/managers/router/radix_cache.py

@@ -11,6 +11,7 @@ class TreeNode:
     def __init__(self):
         self.children = defaultdict(TreeNode)
         self.parent = None
+        self.key = None
         self.value = None
         self.ref_counter = 0
         self.last_access_time = time.time()
@@ -37,6 +38,7 @@ class RadixCache:
 
     def reset(self):
         self.root_node = TreeNode()
+        self.root_node.key = []
         self.root_node.value = []
         self.root_node.ref_counter = 1
         self.evictable_size_ = 0
@@ -115,40 +117,45 @@ class RadixCache:
     ##### Internal Helper Functions #####
     def _match_prefix_helper(self, node, key, value, last_node):
         node.last_access_time = time.time()
-
-        for c_key, child in node.children.items():
-            prefix_len = match(c_key, key)
-            if prefix_len != 0:
-                if prefix_len < len(c_key):
-                    new_node = self._split_node(c_key, child, prefix_len)
+        if len(key) == 0:
+            return
+
+        if key[0] in node.children.keys():
+            child = node.children[key[0]]
+            prefix_len = match(child.key, key)
+            if prefix_len < len(child.key):
+                new_node = self._split_node(child.key, child, prefix_len)
                 value.append(new_node.value)
                 last_node[0] = new_node
             else:
                 value.append(child.value)
                 last_node[0] = child
                 self._match_prefix_helper(child, key[prefix_len:], value, last_node)
-                break
 
     def _split_node(self, key, child, split_len):
         # new_node -> child
         new_node = TreeNode()
-        new_node.children = {key[split_len:]: child}
+        new_node.children = {key[split_len:][0]: child}
         new_node.parent = child.parent
         new_node.ref_counter = child.ref_counter
+        new_node.key = child.key[:split_len]
         new_node.value = child.value[:split_len]
         child.parent = new_node
+        child.key = child.key[split_len:]
         child.value = child.value[split_len:]
-        new_node.parent.children[key[:split_len]] = new_node
-        del new_node.parent.children[key]
+        new_node.parent.children[key[:split_len][0]] = new_node
         return new_node
 
     def _insert_helper(self, node, key, value):
         node.last_access_time = time.time()
+        if len(key) == 0:
+            return 0
 
-        for c_key, child in node.children.items():
-            prefix_len = match(c_key, key)
+        if key[0] in node.children.keys():
+            child = node.children[key[0]]
+            prefix_len = match(child.key, key)
 
-            if prefix_len == len(c_key):
+            if prefix_len == len(child.key):
                 if prefix_len == len(key):
                     return prefix_len
                 else:
@@ -156,8 +163,7 @@ class RadixCache:
                     value = value[prefix_len:]
                     return prefix_len + self._insert_helper(child, key, value)
 
-            if prefix_len:
-                new_node = self._split_node(c_key, child, prefix_len)
+            new_node = self._split_node(child.key, child, prefix_len)
             return prefix_len + self._insert_helper(
                 new_node, key[prefix_len:], value[prefix_len:]
             )
@@ -165,14 +171,15 @@ class RadixCache:
         if len(key):
             new_node = TreeNode()
             new_node.parent = node
+            new_node.key = key
             new_node.value = value
-            node.children[key] = new_node
+            node.children[key[0]] = new_node
             self.evictable_size_ += len(value)
         return 0
 
     def _print_helper(self, node, indent):
-        for key, child in node.children.items():
-            print(" " * indent, len(key), key[:10], f"r={child.ref_counter}")
+        for _, child in node.children.items():
+            print(" " * indent, len(child.key), child.key[:10], f"r={child.ref_counter}")
             self._print_helper(child, indent=indent + 2)
 
     def _delete_leaf(self, node):
@@ -180,7 +187,7 @@ class RadixCache:
             if v == node:
                 break
         del node.parent.children[k]
-        self.evictable_size_ -= len(k)
+        self.evictable_size_ -= len(node.key)
 
     def _total_size_helper(self, node):
         x = len(node.value)