Automated benchmarking in CI

[Methuselah96]

We need to do some performance testing before we release anything to make sure that we haven't regressed in any of the changes we've made. It would also be great if there was a way to do this through CI. In the original repo, it looked like this was done by Lee just saying that something doesn't look fast.

[jdeniau]

It seems like there are performance tests according to CONTRIBUTING.md but as you said, they seemed to be triggered manually.

[Methuselah96]

Yeah, you're right there are already some manual benchmarking tools.

One option (for the upcoming publish) would be to make sure those benchmarks cover the code that we've modified and run them on our changes to make sure we haven't regressed. I don't feel comfortable with releasing what we have so far without doing this step.

But ideally I would like the benchmarking to be done in CI so that we can catch any regressions before the PR gets merged.

[bdurrer]

We discussed automated performance tests and the involved problems on Slack. Because all CI/CD runners are (to a certain extent) virtual, it's hard to compare performance.

So the solution I came up with is to take an unused RasperryPi as test runner. It has defined hardware, no interferring software and therefore the results are reproducible.
My idea is to use github api hooks, run a custom check on every PR which compares the benchmark times against a baseline (e.g. last release or master) and let the runner add the performance diff info add to the PR.

So far I am only 50% done. I'll add the runner code as a repo of immutable-js-oss when it is ready