Serialize vLLM attention profile results

runs/frontier-qwen30-vllm020-profile-v1/profile_vllm020_flashattn.py

@@ -46,6 +46,15 @@ def git_head(repo: Path) -> str:
     ).strip()
 
 
+def json_default(value: object) -> object:
+    if isinstance(value, (Path, torch.dtype, torch.device)):
+        return str(value)
+    item = getattr(value, "item", None)
+    if callable(item):
+        return item()
+    raise TypeError(f"cannot serialize {type(value).__name__}")
+
+
 def main() -> None:
     args = parse_args()
     if vllm.__version__ != VLLM_VERSION:
@@ -161,6 +170,7 @@ def main() -> None:
                         "error": result.error,
                     },
                     sort_keys=True,
+                    default=json_default,
                 ),
                 flush=True,
             )
@@ -183,7 +193,9 @@ def main() -> None:
         "rows": rows,
     }
     args.output.parent.mkdir(parents=True, exist_ok=True)
-    args.output.write_text(json.dumps(payload, indent=2, sort_keys=True) + "\n")
+    args.output.write_text(
+        json.dumps(payload, indent=2, sort_keys=True, default=json_default) + "\n"
+    )
 
 
 if __name__ == "__main__":