Add /createRoom benchmarks and fix the template DB under the Rust driver

`tests/rest/client/bench_createroom.py` times room creation per room in
the trial harness, with optional cProfile dumps and per-room counts of
database interactions and SQL statements. It skips unless
`SYNAPSE_BENCH_CREATEROOM` is set.

`scripts-dev/createroom_bench.py` times it against a real server, reusing
`persist_bench.Server`. That server now lifts the room-creation rate limit
and can run on psycopg2 instead of the native driver.

The test template database's maintenance connection now always uses
psycopg2, as `setup_test_homeserver` does. The Rust driver's `postgres`
module has no `connect`, so it failed under `SYNAPSE_TEST_RUST_DRIVER=1`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PVLsNh6akt4ifEizY4D1ta

scripts-dev/createroom_bench.py

@@ -0,0 +1,139 @@
+#!/usr/bin/env python
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2026 Element Creations Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl-3.0.html>.
+#
+
+"""Time `/createRoom` against a real Synapse on Postgres.
+
+Starts the server the way `persist_bench.py` does, once per
+`rust_event_persistence` level. For each scenario it creates five warm-up
+rooms, then `--rooms` rooms one after another, and reports the mean and median
+request time and the CPU of the reactor thread and of the process per room.
+
+    poetry run python scripts-dev/createroom_bench.py --levels off,full
+
+`--psycopg2` runs the server on psycopg2 instead of the native driver.
+"""
+
+import argparse
+import json
+import os
+import statistics
+import sys
+import tempfile
+import time
+from typing import Any
+
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+
+import persist_bench as pb  # noqa: E402
+
+SCENARIOS: dict[str, dict[str, Any]] = {
+    "plain": {},
+    "private_invite": {"preset": "private_chat", "invite": ["@invitee:bench"]},
+    "public_named": {"preset": "public_chat", "name": "Bench room", "topic": "A topic"},
+    "initial_state": {
+        "initial_state": [
+            {
+                "type": "m.room.encryption",
+                "state_key": "",
+                "content": {"algorithm": "m.megolm.v1.aes-sha2"},
+            },
+            {
+                "type": "m.room.guest_access",
+                "state_key": "",
+                "content": {"guest_access": "can_join"},
+            },
+            {
+                "type": "m.space.child",
+                "state_key": "!a:bench",
+                "content": {"via": ["bench"]},
+            },
+            {
+                "type": "m.space.child",
+                "state_key": "!b:bench",
+                "content": {"via": ["bench"]},
+            },
+        ]
+    },
+}
+
+CREATE_ROOM = "/_matrix/client/v3/createRoom"
+
+
+def bench_level(level: str, rooms: int, rust_driver: bool) -> list[dict[str, Any]]:
+    results = []
+    workdir = tempfile.mkdtemp(prefix=f"createroom-bench-{level}-")
+    server = pb.Server(level, workdir, rust_driver=rust_driver)
+    try:
+        server.start()
+        token = pb.register("creator")
+        pb.register("invitee")
+        for name, body in SCENARIOS.items():
+            for _ in range(5):
+                pb.ok("POST", CREATE_ROOM, body, token)
+            before = server.sample()
+            times = []
+            for _ in range(rooms):
+                t0 = time.perf_counter()
+                pb.ok("POST", CREATE_ROOM, body, token)
+                times.append(time.perf_counter() - t0)
+            after = server.sample()
+            row = {
+                "level": level,
+                "scenario": name,
+                "mean_ms": 1000 * statistics.mean(times),
+                "p50_ms": 1000 * statistics.median(times),
+                "reactor_cpu_ms": 1000
+                * (after.reactor_cpu - before.reactor_cpu)
+                / rooms,
+                "process_cpu_ms": 1000
+                * (after.process_cpu - before.process_cpu)
+                / rooms,
+            }
+            results.append(row)
+            print(row, flush=True)
+    finally:
+        server.stop()
+    return results
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--levels", default="off,full")
+    parser.add_argument("--rooms", type=int, default=40)
+    parser.add_argument("--psycopg2", action="store_true")
+    parser.add_argument("--json", help="also write the results to this file")
+    args = parser.parse_args()
+
+    results = []
+    for level in args.levels.split(","):
+        results += bench_level(level, args.rooms, rust_driver=not args.psycopg2)
+
+    print(
+        f"\n{'scenario':<16} {'level':<12} {'mean ms':>8} {'p50 ms':>8}"
+        f" {'reactor ms':>11} {'process ms':>11}"
+    )
+    for r in results:
+        print(
+            f"{r['scenario']:<16} {r['level']:<12} {r['mean_ms']:>8.1f}"
+            f" {r['p50_ms']:>8.1f} {r['reactor_cpu_ms']:>11.1f}"
+            f" {r['process_cpu_ms']:>11.1f}"
+        )
+    if args.json:
+        with open(args.json, "w") as f:
+            json.dump(results, f, indent=2)
+
+
+if __name__ == "__main__":
+    main()

scripts-dev/persist_bench.py

@@ -120,9 +120,10 @@ def _metrics() -> dict[str, float]:
 class Server:
     """A Synapse process on its own database."""
 
-    def __init__(self, level: str, workdir: str) -> None:
+    def __init__(self, level: str, workdir: str, rust_driver: bool = True) -> None:
         self.level = level
         self.workdir = workdir
+        self.rust_driver = rust_driver
         self.database = f"persist_bench_{level}_{secrets.token_hex(3)}"
         self.process: subprocess.Popen | None = None
 
@@ -153,7 +154,7 @@ class Server:
             ],
             "database": {
                 "name": "psycopg2",
-                "use_rust_driver": True,
+                "use_rust_driver": self.rust_driver,
                 "args": {
                     "database": self.database,
                     "host": os.environ.get("PGHOST", "localhost"),
@@ -171,6 +172,7 @@ class Server:
             },
             "rc_joins_per_room": {"per_second": 100000, "burst_count": 100000},
             "rc_registration": {"per_second": 100000, "burst_count": 100000},
+            "rc_room_creation": {"per_second": 100000, "burst_count": 100000},
             "rc_login": {
                 "address": {"per_second": 100000, "burst_count": 100000},
                 "account": {"per_second": 100000, "burst_count": 100000},