potiuk commented on a change in pull request #18356:
URL: https://github.com/apache/airflow/pull/18356#discussion_r712916297



##########
File path: docs/apache-airflow/best-practices.rst
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@@ -255,9 +297,34 @@ No additional code needs to be written by the user to run 
this test.
 
 .. code-block:: bash
 
- python your-dag-file.py
+     python your-dag-file.py
+
+Running the above command without any error ensures your DAG does not contain 
any uninstalled dependency,
+syntax errors, etc. Make sure that you load your DAG in an environment that 
corresponds to your
+scheduler environment - with the same dependencies, environment variables, 
common code referred from the
+DAG.
+
+This is also a great way to check if your DAG loads faster after an 
optimization, if you want to attempt
+to optimize DAG loading time. Simply run the DAG and measure the time it 
takes, but again you have to
+make sure your DAG runs with the same dependencies, environment variables, 
common code.
+Make sure to run it several time in succession to account for caching effects. 
Compare the results
+before and after the optimization in order to assess the impact of the 
optimization.
+
+There are many ways to measure the time of processing, one of them in Linux 
environment is to
+use built-in ``time`` command
+
+.. code-block:: bash
+
+     time python your-dag-file.py
+
+Result:
+
+.. code-block:: text
+
+     python your-dag-file.py 0.05s user 0.02s system 1% cpu 1.033 total
 
-Running the above command without any error ensures your DAG does not contain 
any uninstalled dependency, syntax errors, etc.
+The important metrics is the "total time" - which tells you how long elapsed 
time it took
+to process the DAG.

Review comment:
       Thought about it, yeah. Might be worth mentioning indeed (though I tried 
to be quite clear here that it's about the "improvements" indeed it's good to 
make this statement.




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