Add benchmark for blocking time reading chunks

tests/test_benchmarks_web_functional.py

@@ -0,0 +1,39 @@
+import asyncio
+from collections.abc import Iterator
+from unittest import mock
+
+from pytest_codspeed import BenchmarkFixture
+
+from aiohttp import web
+from aiohttp.pytest_plugin import AiohttpClient
+
+
+async def test_read_many_chunks(
+    aiohttp_client: AiohttpClient, benchmark: BenchmarkFixture
+) -> None:
+    """Benchmark blocking time when receiving many small chunks."""
+
+    async def sender() -> Iterator[bytes]:
+        for _ in range(200000):
+            yield b"x"
+
+    async def handle(request: web.Request) -> web.Response:
+        # Wait until buffer is full and reading gets paused.
+        while not request.protocol._reading_paused:
+            await asyncio.sleep(0.01)
+
+        # We want to measure the initial blocking time in this call.
+        # Mocking out the ._wait() call forces the method to return at the first wait,
+        # without waiting for more data or processing the rest of the body.
+        with mock.patch.object(request.content, "_wait", autospec=True):
+            chunk = await benchmark(request.read)
+
+        return web.Response(text=str(len(chunk)))
+
+    app = web.Application()
+    app.router.add_post("/", handle)
+    client = await aiohttp_client(app)
+
+    async with client.post("/", chunked=True, data=sender()) as resp:
+        assert resp.status == 200
+        assert int(await resp.text()) > 100