[tune] Fixup exception messages (#5238)

python/ray/tune/trainable.py

@@ -26,6 +26,8 @@ from ray.tune.util import UtilMonitor
 
 logger = logging.getLogger(__name__)
 
+SETUP_TIME_THRESHOLD = 10
+
 
 class Trainable(object):
     """Abstract class for trainable models, functions, etc.
@@ -93,7 +95,14 @@ class Trainable(object):
         self._timesteps_since_restore = 0
         self._iterations_since_restore = 0
         self._restored = False
+        start_time = time.time()
         self._setup(copy.deepcopy(self.config))
+        setup_time = time.time() - start_time
+        if setup_time > SETUP_TIME_THRESHOLD:
+            logger.info("_setup took {:.3f} seconds. If your trainable is "
+                        "slow to initialize, consider setting "
+                        "reuse_actors=True to reduce actor creation "
+                        "overheads.".format(setup_time))
         self._local_ip = ray.services.get_node_ip_address()
         self._monitor = UtilMonitor(start=log_sys_usage)