(Merge 3.4) asyncio, Tulip issue 172: only log selector timing in debug mode

Lib/asyncio/base_events.py

@@ -834,8 +834,7 @@ class BaseEventLoop(events.AbstractEventLoop):
             when = self._scheduled[0]._when
             timeout = max(0, when - self.time())
 
-        # TODO: Instrumentation only in debug mode?
-        if logger.isEnabledFor(logging.INFO):
+        if self._debug:
             t0 = self.time()
             event_list = self._selector.select(timeout)
             dt = self.time() - t0

Lib/test/test_asyncio/test_base_events.py

@@ -247,6 +247,9 @@ class BaseEventLoopTests(test_utils.TestCase):
             time.sleep(1.0)
             return []
 
+        # logging needs debug flag
+        self.loop.set_debug(True)
+
         # Log to INFO level if timeout > 1.0 sec.
         self.loop._selector.select = slow_select
         self.loop._process_events = mock.Mock()