[ perf ] Replace json-> orjson in hot path (#11221)

Signed-off-by: vincentzed <207368749+vincentzed@users.noreply.github.com>

python/sglang/srt/sampling/custom_logit_processor.py

@@ -4,6 +4,7 @@ from functools import lru_cache
 from typing import Any, Dict, List, Optional
 
 import dill
+import orjson
 import torch
 
 
@@ -12,7 +13,7 @@ def _cache_from_str(json_str: str):
     """Deserialize a json string to a Callable object.
     This function is cached to avoid redundant deserialization.
     """
-    data = json.loads(json_str)
+    data = orjson.loads(json_str)
     return dill.loads(bytes.fromhex(data["callable"]))