From 790c1bc2519703b547ce6f16daa7a9f58857c00a Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sun, 13 Aug 2023 19:37:45 -0500
Subject: [PATCH] Decrease event loop latency by binding time.monotonic to
 loop.time directly (#98288)

* Decrease event loop latency by binding time.monotonic to loop.time directly

This is a small improvment to decrease event loop latency. While the goal is
is to reduce Bluetooth connection time latency, everything using asyncio
is a bit more responsive as a result.

* relo per comments

* fix too fast by adding resolution, ensure monotonic time is patchable by freezegun

* fix test that freezes time too late and has a race loop
---
 homeassistant/runner.py                    | 5 +++++
 tests/common.py                            | 5 ++++-
 tests/components/statistics/test_sensor.py | 7 +++++--
 tests/patch_time.py                        | 9 ++++++++-
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/homeassistant/runner.py b/homeassistant/runner.py
index 4bbf1a7dada0..ed49db37f971 100644
--- a/homeassistant/runner.py
+++ b/homeassistant/runner.py
@@ -8,6 +8,7 @@ import logging
 import os
 import subprocess
 import threading
+from time import monotonic
 import traceback
 from typing import Any
 
@@ -114,6 +115,10 @@ class HassEventLoopPolicy(asyncio.DefaultEventLoopPolicy):
         loop.set_default_executor = warn_use(  # type: ignore[method-assign]
             loop.set_default_executor, "sets default executor on the event loop"
         )
+        # bind the built-in time.monotonic directly as loop.time to avoid the
+        # overhead of the additional method call since its the most called loop
+        # method and its roughly 10%+ of all the call time in base_events.py
+        loop.time = monotonic  # type: ignore[method-assign]
         return loop
 
 
diff --git a/tests/common.py b/tests/common.py
index eb8c8417f16e..0431743cccf8 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -420,6 +420,9 @@ def async_fire_time_changed(
     _async_fire_time_changed(hass, utc_datetime, fire_all)
 
 
+_MONOTONIC_RESOLUTION = time.get_clock_info("monotonic").resolution
+
+
 @callback
 def _async_fire_time_changed(
     hass: HomeAssistant, utc_datetime: datetime | None, fire_all: bool
@@ -432,7 +435,7 @@ def _async_fire_time_changed(
             continue
 
         mock_seconds_into_future = timestamp - time.time()
-        future_seconds = task.when() - hass.loop.time()
+        future_seconds = task.when() - (hass.loop.time() + _MONOTONIC_RESOLUTION)
 
         if fire_all or mock_seconds_into_future >= future_seconds:
             with patch(
diff --git a/tests/components/statistics/test_sensor.py b/tests/components/statistics/test_sensor.py
index 4b77e2d07253..780e550f2242 100644
--- a/tests/components/statistics/test_sensor.py
+++ b/tests/components/statistics/test_sensor.py
@@ -8,6 +8,7 @@ from typing import Any
 from unittest.mock import patch
 
 from freezegun import freeze_time
+import pytest
 
 from homeassistant import config as hass_config
 from homeassistant.components.recorder import Recorder
@@ -1286,12 +1287,14 @@ async def test_initialize_from_database(
     assert state.attributes.get(ATTR_UNIT_OF_MEASUREMENT) == UnitOfTemperature.CELSIUS
 
 
+@pytest.mark.freeze_time(
+    datetime(dt_util.utcnow().year + 1, 8, 2, 12, 23, 42, tzinfo=dt_util.UTC)
+)
 async def test_initialize_from_database_with_maxage(
     recorder_mock: Recorder, hass: HomeAssistant
 ) -> None:
     """Test initializing the statistics from the database."""
-    now = dt_util.utcnow()
-    current_time = datetime(now.year + 1, 8, 2, 12, 23, 42, tzinfo=dt_util.UTC)
+    current_time = dt_util.utcnow()
 
     # Testing correct retrieval from recorder, thus we do not
     # want purging to occur within the class itself.
diff --git a/tests/patch_time.py b/tests/patch_time.py
index 2a453053170f..5f5dc467c9d9 100644
--- a/tests/patch_time.py
+++ b/tests/patch_time.py
@@ -2,8 +2,9 @@
 from __future__ import annotations
 
 import datetime
+import time
 
-from homeassistant import util
+from homeassistant import runner, util
 from homeassistant.util import dt as dt_util
 
 
@@ -12,5 +13,11 @@ def _utcnow() -> datetime.datetime:
     return datetime.datetime.now(datetime.UTC)
 
 
+def _monotonic() -> float:
+    """Make monotonic patchable by freezegun."""
+    return time.monotonic()
+
+
 dt_util.utcnow = _utcnow  # type: ignore[assignment]
 util.utcnow = _utcnow  # type: ignore[assignment]
+runner.monotonic = _monotonic  # type: ignore[assignment]