diff --git a/benchmarks/upload_download.py b/benchmarks/upload_download.py
new file mode 100644
index 000000000..bd1b08e7a
--- /dev/null
+++ b/benchmarks/upload_download.py
@@ -0,0 +1,94 @@
+"""
+First attempt at benchmarking uploads and downloads.
+
+To run:
+
+$ pytest benchmarks/upload_download.py  -s -v -Wignore
+
+TODO Parameterization (pytest?)
+- Foolscap vs not foolscap
+- Number of nodes
+- Data size
+- Number of needed/happy/total shares.
+"""
+
+from time import time, process_time
+from contextlib import contextmanager
+from tempfile import mkdtemp
+import os
+
+from twisted.trial.unittest import TestCase
+
+from allmydata.util.deferredutil import async_to_deferred
+from allmydata.util.consumer import MemoryConsumer
+from allmydata.test.common_system import SystemTestMixin
+from allmydata.immutable.upload import Data as UData
+from allmydata.mutable.publish import MutableData
+
+
+@contextmanager
+def timeit(name):
+    start = time()
+    start_cpu = process_time()
+    try:
+        yield
+    finally:
+        print(
+            f"{name}: {time() - start:.3f} elapsed, {process_time() - start_cpu:.3f} CPU"
+        )
+
+
+class ImmutableBenchmarks(SystemTestMixin, TestCase):
+    """Benchmarks for immutables."""
+
+    # To use Foolscap, change to True:
+    FORCE_FOOLSCAP_FOR_STORAGE = False
+
+    @async_to_deferred
+    async def setUp(self):
+        SystemTestMixin.setUp(self)
+        self.basedir = os.path.join(mkdtemp(), "nodes")
+
+        # 2 nodes
+        await self.set_up_nodes(2)
+
+        # 1 share
+        for c in self.clients:
+            c.encoding_params["k"] = 1
+            c.encoding_params["happy"] = 1
+            c.encoding_params["n"] = 1
+
+        print()
+
+    @async_to_deferred
+    async def test_upload_and_download_immutable(self):
+        # To test larger files, change this:
+        DATA = b"Some data to upload\n" * 10
+
+        for i in range(5):
+            # 1. Upload:
+            with timeit("  upload"):
+                uploader = self.clients[0].getServiceNamed("uploader")
+                results = await uploader.upload(UData(DATA, convergence=None))
+
+            # 2. Download:
+            with timeit("download"):
+                uri = results.get_uri()
+                node = self.clients[1].create_node_from_uri(uri)
+                mc = await node.read(MemoryConsumer(), 0, None)
+                self.assertEqual(b"".join(mc.chunks), DATA)
+
+    @async_to_deferred
+    async def test_upload_and_download_mutable(self):
+        # To test larger files, change this:
+        DATA = b"Some data to upload\n" * 10
+
+        for i in range(5):
+            # 1. Upload:
+            with timeit("  upload"):
+                result = await self.clients[0].create_mutable_file(MutableData(DATA))
+
+            # 2. Download:
+            with timeit("download"):
+                data = await result.download_best_version()
+                self.assertEqual(data, DATA)
diff --git a/newsfragments/3952.minor b/newsfragments/3952.minor
new file mode 100644
index 000000000..e69de29bb