Bug 165869

Summary: [CSS Parser] Enable CSS Deferred Parsing
Product: WebKit Reporter: Dave Hyatt <hyatt>
Component: CSSAssignee: Dave Hyatt <hyatt>
Status: REOPENED ---    
Severity: Normal CC: barraclough, commit-queue
Priority: P2    
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Description Flags
Patch none

Description Dave Hyatt 2016-12-14 14:21:35 PST
This bug is tracking turning on CSS deferred parsing by default. I'm going to post some performance numbers to make it clear what a win it is.
Comment 1 Dave Hyatt 2016-12-14 14:53:27 PST
Some #s. All are done on reloads of the page to ensure all stylesheets reparse. 10 loads done of each site with deferred parsing on and off and average taken.

40% reduction on apple.com
25% reduction on twitter.com (logged in with a feed)
25% reduction on facebook.com (logged in, my account)
30% reduction on cnn.com

The gain is anywhere from 5-15ms for each page in the examples above. Parsing doesn't take all that long on most pages, but even so, this is a huge improvement.
Comment 2 Dave Hyatt 2016-12-14 15:25:18 PST
Created attachment 297136 [details]
Comment 3 Sam Weinig 2016-12-14 16:11:26 PST
Comment on attachment 297136 [details]

Nice nice!
Comment 4 WebKit Commit Bot 2016-12-15 07:46:49 PST
Comment on attachment 297136 [details]

Clearing flags on attachment: 297136

Committed r209862: <http://trac.webkit.org/changeset/209862>
Comment 5 WebKit Commit Bot 2016-12-15 07:46:53 PST
All reviewed patches have been landed.  Closing bug.
Comment 6 Gavin Barraclough 2016-12-19 16:06:50 PST
Reverted in r209997 due to performance regressions.