1054779 - Loading specific websites blocks user interface for > 10s

Status: RESOLVED DUPLICATE of bug 516752

(Firefox :: Untriaged, defect)

Description

[Clemens Eisserer]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Firefox/31.0 (Beta/Release)
Build ID: 20140716183446

Steps to reproduce:

Loaded http://torstatus.blutmagie.de/


Actual results:

Firefox' userinterface was almost blocked (the loading indicator was updated every 2s, but no response to clicks) for > 10s on my fast Core i7 notebook.

On my mother's Pentium-4 notebook, firefox was not responding to user interaction for a few minutes, with the tab.loading indicator updated every ~10s.
Moving other windows on top of FF, left the FF window blank, up until a dozen seconds later FF managed to repaint itself.
On that slow machine loading gmail in a tab while trying to browse in another tab results in the same stall - blocking the whole browser window for several seconds (the same stall occurs with my i7 notebook, however there it only takes 1-2s).

Other browser such as chrome handle this fine, as their user interface doesn't seem to be dependent on the rendering engine that much.


Expected results:

during parsing and rendering the page, firefox should have stayed responsive in regard to user interaction - as chrome, opera and internet explorer do.

Comment 1

[Daniel Holbert [:dholbert]]

Traditionally, Firefox is single-process & essentially single-threaded. In particular, it uses a single thread to render JavaScript and render sites and render the UI.  When a particular operation takes too long, this can lead to hangups like you describe, and block it from repainting the UI and responding to user input. 

Good news, though - there's a project underway to render the UI in its own process, so that it will stay responsive in cases like this.  This project is codenamed "Electrolysis" or "e10s".  More information is available here: https://wiki.mozilla.org/Electrolysis

This project is being tracked in bug 516752, so I'm marking this as a duplicate of that bug.

Comment 2

[Clemens Eisserer]

Well, I've heard of electrolysis *years* ago and from time to time follow its progress - but it doesn't seem there is a lot happening there...

Comment 3

[Daniel Holbert [:dholbert]]

It was de-prioritized for several years, after we got as far as shifting plugins into their own process. In the last ~6 months, though, it's been stepped up and has a team actively working on it.

If you want to test the current state, you can install Firefox Nightly and use "File | New e10s Window".