Change PythonMessage's signature (#402)

Summary:
Pull Request resolved: #402

`&[u8]` is much faster than `Vec<u8>` for some reason (See V1 of this diff for comparision). *probably* because:

`Vec<u8>` is mapped to pyo3's `PySequence`, and then it does this under the hood: https://fburl.com/code/6cw3osxf

`&[u8]` is just a pointer to rust, then rust does `memcpy` under the hood, which is much faster.

Reviewed By: moonli, shayne-fletcher

Differential Revision: D77594166

fbshipit-source-id: f296c32ae0539e59391f142b8fb4b236f0dfedc7

Author: pzhan9

monarch_hyperactor/src/actor.rs

@@ -208,7 +208,7 @@ impl PythonMessage {
     #[pyo3(signature = (method, message, response_port, rank))]
     fn new(
         method: String,
-        message: Vec<u8>,
+        message: &[u8],
         response_port: Option<EitherPortRef>,
         rank: Option<usize>,
     ) -> Self {

python/tests/_monarch/test_actor.py

@@ -0,0 +1,24 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# pyre-strict
+
+import time
+
+from monarch._rust_bindings.monarch_hyperactor.actor import PythonMessage
+
+
+def test_python_message() -> None:
+    """
+    Verifies that PythonMessage can be constructed reasonably fast.
+    """
+    method: str = "test_method"
+    payload: str = "a" * 2**30  # 1gb
+    blob: bytes = payload.encode("utf-8")
+    t = time.time()
+    PythonMessage(method, blob, None, None)
+    t_spent = time.time() - t
+    assert t_spent < 1