Bug 145899

Summary: Poor scrolling performance with large complex table
Product: WebKit Reporter: Gavin Sherlock <gsherloc>
Component: TablesAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: cdumez, kling, koivisto, simon.fraser, zalan
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
URL: http://www.yeastgenome.org/cgi-bin/FUNGI/alignment.pl?locus=YBR140C

Description Gavin Sherlock 2015-06-11 14:57:47 PDT 
Go to bug url (http://www.yeastgenome.org/cgi-bin/FUNGI/alignment.pl?locus=YBR140C)
Wait for page to load
Scroll down

Expected results:

Smooth scrolling through the document

Actual results:

Often shows no rendered content for several seconds, pauses, stutters and locks up

Tested with release Safari and r185452
Comment 1 zalan 2015-06-11 22:34:17 PDT 
This is a table heavy page. I bet that's the reason why the Web process locks up.

66 <table>
2500 <tr>
150K <td>
123K <tt>

Chromes handles it relatively okay. (better than WebKit trunk)
Comment 2 zalan 2015-06-12 08:29:33 PDT 
While loading the page we spend significant amount of time in 
pumpTokenizer (28%) -> SegmentedString::operator= (25%)
and WTF::Deque<SegmentedSubString>::destroyAll (11%)
Also Style::resolveTree() (11%)
After finished loading another round of style resolving kicks in with Style::resolve(37.2%) -> getUncachedPseudoStyle(13%)
While scrolling, we spend most of the time in cell painting -> text drawing.