1853495 - Online JS AST viewer spends 4min+ around GC. Chrome will crash.

Status: NEW

(Core :: JavaScript Engine, task, P3)

Description

[Mayank Bansal]

Go to https://prettier.io/playground/
In the left pane where the options are, scroll to the bottom.
Un-Select "Show AST" (if it is selected)
Copy and paste the sample JS text.
Select "Show AST"

Nightly : https://share.firefox.dev/48gYd0K (240 seconds and still running)
Chrome: Crashes after a few seconds

We dont crash, so I guess we are technically better than Chrome. But I am filing this bug in case there is some room for improvement.

Comment 1

[Mayank Bansal]

Attachment: d3.txt

Sample JS text

Comment 2

[Mayank Bansal]

For a more reasonable JS code, here are the profiles:

Nightly: https://share.firefox.dev/3ZmROgL
Chrome: https://share.firefox.dev/3LrMoLp

Comment 3

[Mayank Bansal]

Attachment: More reasonably sized JS code

Comment 4

[Mayank Bansal]

I tested on a Nightly from Jan2021. That build had continuous memory increase and reached 7GB+ before I quit the browser.
So our behaviour has improved from before in the sense that we will not OOM and crash.

Comment 5

[Jon Coppeard (:jonco)]

GC scheduling in web workers leaves a lot to be desired, and it looks like this is causing us problems in the first profile.

Comment 6

[Mayank Bansal]

I tried disabling service workers by setting dom.serviceWorkers.enabled=False in a new profile and then visitng the test page. But even then the JS execution was run in a DOM worker per profiler.
So if there is a way to disable SWs and force the page to run JS on the main thread, I would be happy to do that and post results here.

Comment 7

[Mayank Bansal]

Profile with latest Nightly: https://share.firefox.dev/3THbKbo / https://share.firefox.dev/3IYM8lx