doc: add load profile samples to Open Model Thread Group documentation

Author: vlsi

xdocs/usermanual/component_reference.xml

@@ -6521,17 +6521,39 @@ See <a href="get-started.html#classpath">JMeter's Classpath</a> and
        The users are generated according to the schedule.
     </p>
     <p>The load profile consists of a sequence of constant, increasing or decreasing load.
-       The following commands are available:
+       The basic configuration is <code>rate(1/sec) random_arrivals(2 min) rate(3/sec)</code> which means the load will increase linearly
+        from 1 request per second to 3 requests per second during 2-minute timeframe.
+       If you omit "end" rate, then it will be set to the same value as "start". For example,
+        <code>rate(1/sec) random_arrivals(2 min)</code> is exactly the same as <code>rate(1/sec) random_arrivals(2 min) rate(1/sec)</code>.
+       That is why <code>rate(1/sec) random_arrivals(2 min) random_arrivals(3 min) rate(4/sec)</code> is exactly the same as
+        <code>rate(1/sec) random_arrivals(2 min) rate(1/sec) random_arrivals(3 min) rate(4/sec)</code>, so the load is 1/sec during the first two minutes,
+        and then it increases linearly from 1/sec to 4/sec during 3 minutes.
+    </p>
+    <p>Here are examples for using the schedule:
+        <ul>
+            <li><code>rate(10/sec) random_arrivals(1 min) rate(10/sec)</code> &mdash; constant load rate of 10/sec during 1 minute</li>
+            <li><code>rate(0) random_arrivals(1 min) rate(10/sec)</code> &mdash; linearly increase the load from 0 to 10/sec during 1 minute</li>
+            <li><code>rate(0) random_arrivals(1 min) rate(10/sec) random_arrivals(1 min) rate(10/sec) random_arrivals(1 min) rate(0)</code> &mdash;
+                linearly increase the load from 0 to 10/sec during 1 minute, then hold the load during 1 minute,
+                then linearly decrease the load from 10/sec to 0 during 1 minute</li>
+            <li><code>rate(10) random_arrivals(1 min) rate(10/sec) random_arrivals(1 min) rate(10/sec) random_arrivals(1 min) rate(0)</code> &mdash;
+                linearly increase the load from 0 to 10/sec during 1 minute, then hold the load during 1 minute,
+                then linearly decrease the load from 10/sec to 0 during 1 minute</li>
+            <li><code>rate(10) random_arrivals(1 min) pause(2 sec) random_arrivals(1 min)</code> &mdash;
+                run with constant load of 10 per second during 1 minute, then make 2 second pause, then resume the load of 10 per second for 1 minute</li>
+        </ul>
+    </p>
+    <p>The following commands are available:
         <ul>
             <li><code>rate(&lt;number&gt;/sec)</code> &mdash; configures target load rate.
                 The following time units are supported: <code>ms</code>, <code>sec</code>, <code>min</code>, <code>hour</code>, <code>day</code>.
                 You can omit time unit in case the rate is 0: <code>rate(0)</code></li>
             <li><code>random_arrivals(&lt;number&gt; sec)</code> &mdash; configures random arrivals schedule with the given duration.
                 The starting load rate is configured before <code>random_arrivals</code>, and the finish load rate is configured after <code>random_arrivals</code>.
-                For example, 10 minute test from 5/sec at the beginning till 15/sec at the end could be configured as <code>rate(5/sec) random_arrivals(10 min) rate(15/sec)</code>.
+                For example, 10 minute test from 5/sec at the beginning to 15/sec at the end could be configured as <code>rate(5/sec) random_arrivals(10 min) rate(15/sec)</code>.
                 <br/>The implicit rate at the beginning of the test is 0. If the finish rate is not provided (or if several <code>random_arrivals</code> steps go one after another),
                 then the load is constant. For instance, <code>rate(3/sec) random_arrivals(1 min) random_arrivals(2 min) rate(6/sec)</code> configures
-                constant rate of 3/sec for the first 1 minute, and then the load increases from 3/sec till 6/sec during the next 2 minutes.
+                constant rate of 3/sec for the first 1 minute, and then the load increases from 3/sec to 6/sec during the next 2 minutes.
                 The time units are the same as in <code>rate</code>.
             </li>
             <li><code>even_arrivals(&lt;number&gt; sec)</code> &mdash; configures even arrivals (TODO: not implemented yet). For instance, if the desired load