1657176 - The sourcemap worker uses too much CPU

Status: NEW

(DevTools :: General, defect, P3)

Description

[Julien Wajsberg [:julienw]]

I realized today that the sourcemap worker takes a lot of CPU on my computer. This is visible using about:performance.
This happens even though I don't use the devtools window nor the website (of course the devtools are opened).

This was happening on the profiler development server for example.

I believe the worker should be more peaceful, notably when the debugged tab isn't in foreground.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:Honza, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 2

[Jan Honza Odvarko [:Honza] (always need-info? me)]

Julien, can you share the page you used (assuming a page with rather bigger source maps) when noticing the data in about:performance?

Honza

Comment 3

[Julien Wajsberg [:julienw]]

I noticed this on the profiler server, especially on the development server but I just looked at the production server and this seems to happen there too:

1. go to https://profiler.firefox.com
2. check about:performance => notice that no worker dedicated to source maps is present
3. open the devtools (console panel or debugger panel, where source maps are needed)
4. check about:performance again => notice that the worker dedicated to source maps is present and takes quite some time

If you open more tabs you'll notice that there are several instances of that worker, even if the tab is in background and doesn't do much.

Comment 4

[Julien Wajsberg [:julienw]]

I've seen a similar issue when I was opening the devtools on a MDN page.

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.