Improve performance of keepalive rescheduling

CHANGES/8662.misc.rst

@@ -0,0 +1,3 @@
+Reduce frequency of HTTP keep-alive checks -- by :user:`bdraco`.
+
+Previously, when processing a request for a keep-alive connection, the keep-alive check would happen every second; the check now occurs when the keep-alive is expected to timeout or 1s later, whichever is later.

aiohttp/web_protocol.py

@@ -448,17 +448,19 @@ def _process_keepalive(self) -> None:
             return
 
         next = self._keepalive_time + self._keepalive_timeout
+        now = self._loop.time()
 
         # handler in idle state
-        if self._waiter:
-            if self._loop.time() > next:
-                self.force_close()
-                return
+        if self._waiter and now > next:
+            self.force_close()
+            return
 
         # not all request handlers are done,
-        # reschedule itself to next second
-        self._keepalive_handle = self._loop.call_later(
-            self.KEEPALIVE_RESCHEDULE_DELAY,
+        # reschedule itself to next or
+        # the next second, whichever is later
+        reschedule_time = max(next, now + self.KEEPALIVE_RESCHEDULE_DELAY)
+        self._keepalive_handle = self._loop.call_at(
+            reschedule_time,
             self._process_keepalive,
         )