[FEATURE] support custom vllm tuned config path for fused moe triton kernels (#22791)

Signed-off-by: Chi Zhang <zhangchi.usc1992@bytedance.com>

vllm/envs.py

@@ -158,6 +158,7 @@ if TYPE_CHECKING:
     VLLM_USE_TRTLLM_ATTENTION: Optional[str] = None
     VLLM_USE_FLASHINFER_MOE_MXFP4_MXFP8: bool = False
     VLLM_USE_FLASHINFER_MOE_MXFP4_BF16: bool = False
+    VLLM_TUNED_CONFIG_FOLDER: Optional[str] = None
 
 
 def get_default_cache_root():
@@ -1120,6 +1121,11 @@ environment_variables: dict[str, Callable[[], Any]] = {
     #    never removed from memory until the server terminates.
     "VLLM_ENABLE_RESPONSES_API_STORE":
     lambda: bool(int(os.getenv("VLLM_ENABLE_RESPONSES_API_STORE", "0"))),
+
+    # Allows vllm to find tuned config under customized folder
+    "VLLM_TUNED_CONFIG_FOLDER":
+    lambda: os.getenv("VLLM_TUNED_CONFIG_FOLDER", None),
+
 }
 
 # --8<-- [end:env-vars-definition]

vllm/model_executor/layers/fused_moe/fused_moe.py

@@ -701,8 +701,20 @@ def get_moe_configs(
     block_shape = [block_n, block_k] if block_n and block_k else None
     json_file_name = get_config_file_name(E, N, dtype, block_shape)
 
-    config_file_path = os.path.join(
+    config_file_paths = []
+
+    # note that we prioritize user defined config
+    user_defined_config_folder = envs.VLLM_TUNED_CONFIG_FOLDER
+    if user_defined_config_folder is not None:
+        user_defined_config_file_path = os.path.join(
+            user_defined_config_folder, json_file_name)
+        config_file_paths.append(user_defined_config_file_path)
+
+    default_config_file_path = os.path.join(
         os.path.dirname(os.path.realpath(__file__)), "configs", json_file_name)
+    config_file_paths.append(default_config_file_path)
+
+    for config_file_path in config_file_paths:
         if os.path.exists(config_file_path):
             with open(config_file_path) as f:
                 logger.info("Using configuration from %s for MoE layer.",
@@ -714,7 +726,7 @@ def get_moe_configs(
     # configuration
     logger.warning(
         ("Using default MoE config. Performance might be sub-optimal! "
-         "Config file not found at %s"), config_file_path)
+         "Config file not found at %s"), config_file_paths)
     return None