Update docs for running locust in Step Load Mode

docs/quickstart.rst

@@ -176,3 +176,7 @@ and point it to http://127.0.0.1:8089 (if you are running Locust locally). Then
 greeted with something like this:
 
 .. image:: images/webui-splash-screenshot.png
+
+If you :ref:`run Locust in Step Load Mode <running-locust-in-step-load-mode>`, then you should be greeted with Locust UI like this:
+
+.. image:: images/webui-stepload-screenshot.png

docs/running-locust-distributed.rst

@@ -103,6 +103,12 @@ Running Locust distributed without the web UI
 See :ref:`running-locust-distributed-without-web-ui`
 
 
+Running Locust distributed in Step Load mode
+=============================================
+
+See :ref:`running-locust-in-step-load-mode`
+
+
 Increase Locust's performance
 =============================
 

docs/running-locust-in-step-load-mode.rst

@@ -0,0 +1,52 @@
+.. _running-locust-in-step-load-mode:
+
+=================================
+Running Locust in Step Load Mode
+=================================
+
+If you want to monitor your service performance with different user load and probe the max tps that can be achieved, you can run Locust with Step Load enabled with ``--step-load``:
+
+.. code-block:: console
+
+    $ locust -f locust_files/my_locust_file.py --step-load
+
+
+Options
+=======
+
+``--step-load``
+------------
+
+Enable Step Load mode to monitor how performance metrics varies when user load increases.
+
+
+``--step-clients``
+-----------
+
+Client count to increase by step in Step Load mode. Only used together with ``--step-load``.
+
+
+``--step-time``
+-------------------------
+
+Step duration in Step Load mode, e.g. (300s, 20m, 3h, 1h30m, etc.). Only used together with ``--step-load``.
+
+
+Running Locust in step load mode without the web UI
+---------------------------------
+
+If you want to run Locust in step load mode without the web UI, you can do that with ``--step-clients`` and ``--step-time``:
+
+.. code-block:: console
+
+    $ locust -f --no-web -c 1000 -r 100 --run-time 1h30m --step-load --step-clients 300 --step-time 20m
+
+Locust will swarm the clients by step and shutdown once the time is up.
+
+
+Running Locust distributed in step load mode
+---------------------------------------------
+
+If you want to :ref:`run Locust distributed <running-locust-distributed>` in step load mode, 
+you should specify the ``--step-load`` option when starting the master node, to swarm locusts by step. It will then show the ``--step-cients`` option and ``--step-time`` option in Locust UI.
+

locust/runners.py

@@ -221,10 +221,10 @@ def start_stepload(self, locust_count, hatch_rate, step_locust_count, step_durat
 
         if self.stepload_greenlet:
             logger.info("There is an ongoing swarming in Step Load mode, will stop it now.")
-            self.greenlet.killone(self.stepload_greenlet)
+            self.stepload_greenlet.kill()
         logger.info("Start a new swarming in Step Load mode: total locust count of %d, hatch rate of %d, step locust count of %d, step duration of %d " % (locust_count, hatch_rate, step_locust_count, step_duration))
         self.state = STATE_INIT
-        self.stepload_greenlet = self.greenlet.spawn(self.stepload_worker)
+        self.stepload_greenlet = gevent.spawn(self.stepload_worker)
         self.stepload_greenlet.link_exception(callback=self.noop)
 
     def stepload_worker(self):