diff -r f35b3a86ade3 Lib/asyncio/base_events.py
--- a/Lib/asyncio/base_events.py	Tue Jan 14 16:48:31 2014 -0600
+++ b/Lib/asyncio/base_events.py	Thu Jan 16 00:12:26 2014 +0100
@@ -96,6 +96,7 @@ class BaseEventLoop(events.AbstractEvent
         self._default_executor = None
         self._internal_fds = 0
         self._running = False
+        self._debug = False
 
     def _make_socket_transport(self, sock, protocol, waiter=None, *,
                                extra=None, server=None):
@@ -609,16 +610,18 @@ class BaseEventLoop(events.AbstractEvent
             else:
                 timeout = min(timeout, deadline)
 
-        # TODO: Instrumentation only in debug mode?
-        t0 = self.time()
-        event_list = self._selector.select(timeout)
-        t1 = self.time()
-        argstr = '' if timeout is None else ' {:.3f}'.format(timeout)
-        if t1-t0 >= 1:
-            level = logging.INFO
+        if self._debug:
+            t0 = self.time()
+            event_list = self._selector.select(timeout)
+            t1 = self.time()
+            argstr = '' if timeout is None else ' {:.3f}'.format(timeout)
+            if t1-t0 >= 1:
+                level = logging.INFO
+            else:
+                level = logging.DEBUG
+            logger.log(level, 'poll%s took %.3f seconds', argstr, t1-t0)
         else:
-            level = logging.DEBUG
-        logger.log(level, 'poll%s took %.3f seconds', argstr, t1-t0)
+            event_list = self._selector.select(timeout)
         self._process_events(event_list)
 
         # Handle 'later' callbacks that are ready.