[Test] Reduce Perf test case and fix modify stage config (#1449)

Signed-off-by: yenuo26 <410167048@qq.com>

tests/conftest.py

@@ -848,41 +848,42 @@ def modify_stage_config(
                 del config[key]
 
     # Apply updates
-    for key, value in updates.items():
-        if key == "stage_args":
-            if value and isinstance(value, dict):
-                stage_args = config.get("stage_args", [])
-                if not stage_args:
-                    raise ValueError("stage_args does not exist in config")
+    if updates:
+        for key, value in updates.items():
+            if key == "stage_args":
+                if value and isinstance(value, dict):
+                    stage_args = config.get("stage_args", [])
+                    if not stage_args:
+                        raise ValueError("stage_args does not exist in config")
 
-                for stage_id, stage_updates in value.items():
-                    # Find stage by ID
-                    target_stage = None
-                    for stage in stage_args:
-                        if stage.get("stage_id") == int(stage_id):
-                            target_stage = stage
-                            break
+                    for stage_id, stage_updates in value.items():
+                        # Find stage by ID
+                        target_stage = None
+                        for stage in stage_args:
+                            if stage.get("stage_id") == int(stage_id):
+                                target_stage = stage
+                                break
 
-                    if target_stage is None:
-                        available_ids = [s.get("stage_id") for s in stage_args if "stage_id" in s]
-                        raise KeyError(f"Stage ID {stage_id} not found, available: {available_ids}")
+                        if target_stage is None:
+                            available_ids = [s.get("stage_id") for s in stage_args if "stage_id" in s]
+                            raise KeyError(f"Stage ID {stage_id} not found, available: {available_ids}")
 
-                    # Apply updates to this stage
-                    for path, val in stage_updates.items():
-                        # Check if this is a simple key (not dot-separated)
-                        # Example: 'engine_input_source' vs 'engine_args.max_model_len'
-                        if "." not in path:
-                            # Direct key assignment (e.g., updating a list value)
-                            target_stage[path] = val
-                        else:
-                            # Dot-separated path (e.g., nested dict access)
-                            apply_update(target_stage, path, val)
-        elif "." in key:
-            # Apply using dot-separated path
-            apply_update(config, key, value)
-        else:
-            # Direct top-level key
-            config[key] = value
+                        # Apply updates to this stage
+                        for path, val in stage_updates.items():
+                            # Check if this is a simple key (not dot-separated)
+                            # Example: 'engine_input_source' vs 'engine_args.max_model_len'
+                            if "." not in path:
+                                # Direct key assignment (e.g., updating a list value)
+                                target_stage[path] = val
+                            else:
+                                # Dot-separated path (e.g., nested dict access)
+                                apply_update(target_stage, path, val)
+            elif "." in key:
+                # Apply using dot-separated path
+                apply_update(config, key, value)
+            else:
+                # Direct top-level key
+                config[key] = value
 
     # Save to new file with timestamp
     timestamp = int(time.time())