1181538 - Scrolling about:addons page is janky

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Mikel]

Attachment: profile.json

User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0
Build ID: 20150707030206

Steps to reproduce:

1) Open about:addons
2) Smooth scroll the page
3) Observe the jank.

A performance recording confirms a lot time spent on painting and style recalculations.
Attaching the profile recording.


Actual results:

Janky scrolling on about:addons page.


Expected results:

Smooth scrolling on about:addons page.

Comment 1

[Virtual_ManPL [:Virtual] 🇵🇱 - (please needinfo? me - so I will see your comment/message/reply/question/etc.)]

Can you still reproduce the issue with latest stable Firefox or latest Nightly?

Comment 2

[Mikel]

Well, the paints and recalculation styles are almost all gone in a new performance recording from the latest Nighlty, but now there are a lot of GC work with a huge "Non-incremental GC" that takes a whooping ~500 ms also when just staying idle on the addons page (and also when scrolling, which janks APZ scrolling of course)!

Note: this seems (I say seems, as I don't see a visual jank of ~500ms while scrolling with APZ) to happen only when recording a performance recording.
Note2: this seems to happen only on internal pages such as the about:addons page and also a "new tab" page (blank page or non blank, doesn't matter), but NOT on tabs with sites where scrolling is smooth and no such GC work.


Attaching a performance recording when staying idle on the about:addons page, and one with smooth scrolling the page (APZ enabled).

Comment 3

[Mikel]

Attachment: profile (idle).json

Comment 4

[Mikel]

Attachment: profile (scrolling).json

Comment 5

[:Gijs (he/him)]

Based on comment #2 and the profiles, is this something the JS team can/should look at? mccr8?

Comment 6

[Terrence Cole [:terrence]]

Moving ni? to Jon.

Comment 7

[Jon Coppeard (:jonco)]

(In reply to Mikel from comment #2)
It's possible that the performance recording triggers extra GCs.  I can see this happening in your supplied profile data, but not for anything like 500ms.

I tried to reproduce this but I don't see any long non-incremental GCs myself.

Since it doesn't seem to happen in normal use I'm going to close this.  Please reopen if you disagree.