1673522 - Slow paint performance | https://projects.fivethirtyeight.com/2020-election-forecast/

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[jim]

+++ This bug was initially created as a clone of Bug #1672880 +++

I closed the original bug prematurely. It turned out to be quite reproducible and not related to other tabs. See video of behavior here: https://drive.google.com/file/d/19d2zlCclqiNRkbn6wGb7QCyg1_328rBr/view?usp=sharing

The page is fast at one size, and once I widen it out it becomes very sluggish. If I shrink the width back down the performance is restored. I don't see a similar slowdown in other browsers.

Original report ------------>

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:82.0) Gecko/20100101 Firefox/82.0

Steps to reproduce:

I've notice sluggish performance on JS-heavy sites compared to Safari and Chrome. One site in particular is dramatically worse: https://projects.fivethirtyeight.com/2020-election-forecast/

Actual results:

Mousing around the simulation graphic (the one with all the dots) takes the better parts of a second to show the pop-up for each dot. According to the profiler, the long pauses are in "Paint" calls.

Expected results:

Both Chrome and Safari show these pop-ups almost instantly.

Comment 1

[Hani Yacoub, Desktop QA]

I confirm that on Firefox the performance of the website is slower comparing to Chrome on Windows 10 x64, MacOS 10.14 and on Ubunutu 20.04.

Comment 2

[Jan de Mooij [:jandem]]

On Mac this performs much better for me with WebRender enabled (Nightly or gfx.webrender.all in about:config in Firefox 82).

Comment 3

[Dzmitry Malyshau [:kvark]]

Marking as S3 as this is fixed by WR, yay!