834589 - Scrolling jank on page due to SelectorMatches and RuleHash:Enumerate

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Mayank Bansal]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130124 Firefox/21.0
Build ID: 20130124054158

Steps to reproduce:

1. Create fresh profile
2. Go to http://www.businessweek.com/articles/2013-01-10/can-meg-whitman-reverse-hewlett-packards-free-fall#r=rss
3. Scroll only a little bit from the top. The main jank is in the top/heading of the page.


Actual results:

jerky scrolling.
Profile : http://people.mozilla.com/~bgirard/cleopatra/#report=96f66898bfc3574c6af2dc20f19415320450b31b

I have seen RuleHash:enumerate and SelectorMatches in numerous profiles i have takes of janky pages.


Expected results:

smoothies.

Comment 1

[Mayank Bansal]

Tentatively marking Snappy, as I have seen RuleHash:enumerate and SelectorMatches in countless profiles  of janky pages.

Comment 2

[Honza Bambas (:mayhemer)]

I am experiencing similar issue with TreeStyleTab when switching between tabs (Fx Beta, 19).  CodeAnalyst tells me:

> Name                                  	Address    	Self 	Children 	Total 	
>  nsFrameManager::ReResolveStyleContext	0x5fa4e680 	30   	2864     	2894  	
>  nsRuleNode::WalkRuleTree             	0x5fa53670 	488  	2054     	2542  	
>  nsStyleSet::GetContext               	0x5fa53040 	6    	2025     	2031  	
>  nsContainerFrame::GetChildLists      	0x5fa778c0 	25   	1534     	1559  	
>  SelectorMatches                      	0x5fa789f0 	404  	932      	1336  	
>
> 5 functions, Total: 953 self samples, 9409 child samples

The total column, as I understand is time in milliseconds.  I am not able to correctly interpret CodeAnalyst results, tho.  However on my relatively fast machine the UI hangs for 1 - 2 seconds and CPU goes to its per-core limit.

Could the suspected job (function) be rewritten to work incrementally to let spin the main loop?

For my case neither e10s nor content thread would help.

Comment 3

[Mayank Bansal]

works Ok-ish for me now.
closing.