Scrolling through Facebook feed is very laggy

[kzar]

Environment

• Adblock Plus 1.13.3 release candidate
• Chrome 59
• No subscriptions, the following filters:

facebook.com#?#.ego_column :-abp-has(.adsCategoryTitleLink)
facebook.com#?#div[id^="hyperfeed_story_id_"] :-abp-has(a[href*="?hc_ref=ADS"])

How to reproduce

1. Browse to ​https://www.facebook.com/ and login.
2. Scroll up and down through your timeline, you'll need to scroll far enough down to trigger the loading of more items.

Observed behaviour

Items in the feed render very slowly, "Page Unresponsive" messages sometimes displayed.

Expected behaviour

Page does not load very slowly, like with Adblock Plus 1.13.2

Background

Facebook is constantly loading new stylesheets as new feed items are being added. This currently makes us reapply all element hiding emulation rules, which takes increasingly long as the document grows. This behavior should be considered a bug because the rules in question don't use :-abp-properties() and so don't depend on stylesheets.

What to change

• When stylesheets change, only reprocess rules that actually depend on styles (:-abp-properties(), also as an inner selector of :-abp-has(... )).
• Don't process stylesheet changes more often than every three seconds - if multiple stylesheets load in quick succession, process them as a batch.

[kzar]

Did I get the details right? I'm going to attempt to reproduce this now.

[kzar]

Bottom-Up performance

[mapx]

I see only 2 rules in easylist with the new feature (both on FB)

facebook.com#?#.ego_column :-abp-has(.adsCategoryTitleLink)
facebook.com#?#div[id^="hyperfeed_story_id_"] :-abp-has(a[href*="?hc_ref=ADS"])

[kzar]

I see only 2 rules in easylist with the new feature (both on FB)

Yep you're right, I can reproduce the problem with only those two filters. I've updated the description.

[trev]

So far the issue seems to be:

• Facebook is constantly loading new stylesheets as new feed items are being added. This currently makes us reapply all element hiding emulation rules, which takes increasingly longer as the document grows.
• This behavior should be considered a bug because the rules in question don't use :-abp-properties() and so don't depend on stylesheets.
• Without this bug these rules wouldn't have any noteworthy effect on Facebook given that in the current iteration our :-abp-has() implementation doesn't consider dynamic changes yet.

[kzar]

Unassigning myself for now since other than reverting these changes I'm not sure how to proceed.

[trev]

Moving to Core, the Platform part is going to be a simple dependency update.

[abpbot]

A commit referencing this issue has landed:
​Issue 5395 - Make sure element hiding emulation doesn't degrade website performance too much

[trev]

Leaving open because this change only landed on a branch for now, it needs to be merged to master as well.

[Ross]

I've tried applying these filters and scrolling through my feed and they don't seem to apply at all/match anything at all. I'm trying to check via the devtools. Am I missing something?

ABP 1.13.2.1786
Chrome 59 / Windows 10

[trev]

No, in build 1786 they aren't supposed to apply any more - the fact that they did before was a bug.

[Ross]

Thanks. This is fixed. Loading more items works fine without anymore than usual lag and the page is never made unresponsive.

ABP 1.13.2.1787
Chrome 51+ / Windows 7
Opera 38+ / Windows 7

[abpbot]

A commit referencing this issue has landed:
​Issue 5395 - Make sure element hiding emulation doesn't degrade website performance too much

[trev]

Landed on master now, only context changed slightly here.