fix: log warning when disable cuda graph (#5209)

python/sglang/srt/model_executor/model_runner.py

@@ -924,6 +924,12 @@ class ModelRunner:
             return
 
         if self.server_args.disable_cuda_graph:
+            logger.warning(
+                "\n\nCUDA Graph is DISABLED.\n"
+                "This will cause significant performance degradation.\n"
+                "CUDA Graph should almost never be disabled in most usage scenarios.\n"
+                "If you encounter OOM issues, please try setting --mem-fraction-static to a lower value (such as 0.8 or 0.7) instead of disabling CUDA Graph.\n"
+            )
             return
 
         tic = time.time()