Documenting profiling of engine startup

distribution/lib/Standard/Base/0.0.0-dev/src/Any.enso

@@ -1,4 +1,5 @@
 import project.Data.Ordering.Ordering
+
 import project.Data.Pair.Pair
 import project.Data.Range.Extensions
 import project.Data.Text.Text

docs/profiler/engine-startup.md

@@ -0,0 +1,35 @@
+# Summary
+
+One of the main objectives to deliver satisfactory user experience
+when using Enso is to be fast when getting ready to work. This requires the engine
+to initialize all services the IDE needs as quickly as possible. In short -
+to **start fast**. This document describes how to measure, record and analyze
+the startup of the Enso engine.
+
+## Collecting the data
+
+Start `project-manager` with following options to record first 20s of
+the Enso engine startup sequence:
+```
+$ project-manager --profiling-events-log-path=start.log --profiling-path=start.npss --profiling-time=20
+```
+Let the IDE connect to just launched `project-manager` - e.g. start the IDE with `--no-backed` option.
+Once the `start.log` and `start.npss` files are generated (next to each other), open them in GraalVM's VisualVM:
+```
+$ graalvm/bin/jvisualvm --openfile start.npss
+```
+Use VisualVM to analyze to recorded data.
+
+### Interactively Analyze
+
+VisualVM offers two timelines. A "stackdepth" one and also _"UI Actions"_ line.
+Hovering over boxes in _"UI Actions"_ shows the messages describing what
+happens in the engine - what has been logged into `start.log`. 
+One can then select an interval and get profiling information for that interval:
+
+![VisualVM](https://user-images.githubusercontent.com/26887752/216099011-33866c1d-06ab-48dc-936d-b9190e80b9fb.png)
+
+This picture shows that 2.7s is spend in `EnsoCompiledJob` task. Overall the 
+goal is to log enough information to help us navigate thru the long startup sequence.
+Select appropriate interval based on the displayed _UI Actions_ - e.g. logged
+events - and analyze what has happened there based on the sampling of JVM stack traces.

docs/profiler/profiling.md

@@ -49,7 +49,8 @@ performing **objective**s.
 
 - **Project startup**  
   Time from selecting a project from the Hello Screen to a working graph view of
-  the project. Sub-processes:
+  the project. See also [engine startup](engine-startup.md) for non-IDE details
+  on a similar topic. Sub-processes:
 
   - **Graph Editor initialization**  
     Time needed to display fully-functional graph editor (not colored).