1512789 - Scrolling inside the kangax table has high latency (Lots of time spent in parent process waiting for APZC)

Status: RESOLVED WORKSFORME

(Core :: Graphics: WebRender, defect, P3)

Description

[Mayank Bansal]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0

Steps to reproduce:

enable WR
Go to https://kangax.github.io/compat-table/esnext/
Scroll till the red table occupies most of the screen
put mouse inside the table, and then try to scroll with the mouse wheel


Actual results:

there is latency while scrolling. Something like when you scroll, it starts slowly, but also ends slowly and scrolls more than what you want to scroll

Profile shows large jank in the parent process, waiting for APZC


Expected results:

not so. non-WR is very smooth

non-WR: https://perfht.ml/2L4rX6W
(despite what the profile may say, scrolling was always very smooth)

WR: https://perfht.ml/2L67b6M

Comment 1

[Mayank Bansal]

Attachment: bandicam 2018-12-08 13-36-11-681.mp4

I scrolled just a tiny bit. But the total amount scrolled was larger than expected, and the scrolling didnt stop when I stopped scrolling.

Comment 2

[Mayank Bansal]

here is a more extreme version : https://perfht.ml/2L3PkgR

could be a dupe of bug 1480964/bug 1497090/bug 1494163 .

Comment 3

[Mayank Bansal]

Another profile : http://bit.ly/2SkCUDm

Could be dupe of other bugs i have filed. Like bug 1527964

Comment 4

[Mayank Bansal]

cant repro anymore.