# 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 in proper order and to make sure the
essential ones are ready 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

### Via the Project Manager

Start `project-manager` with following options to record first 20s of the Enso
engine startup sequence:

```
$ project-manager --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.

### Via the runner

Runner executable also supports the profiling with the `--profiling-path`
option. For example, you can run the Enso project with the profiling enabled:

```
$ enso --profiling-path=/tmp/run.npss --run ~/enso/project/New_Project_1
```

And then open it in the VisualVM:

```
$ visualvm --openfile /tmp/run.npss
```

### 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.