Bug 190105 - Setting a style height value to the existing value still triggers a clone of StyleBoxData and thus slows down RenderStyle::diff
Summary: Setting a style height value to the existing value still triggers a clone of ...
Status: RESOLVED INVALID
Alias: None
Product: WebKit
Classification: Unclassified
Component: CSS (show other bugs)
Version: WebKit Nightly Build
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2018-09-28 20:36 PDT by Simon Fraser (smfr)
Modified: 2018-09-29 16:05 PDT (History)
4 users (show)

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Description Simon Fraser (smfr) 2018-09-28 20:36:19 PDT 
If script keeps setting style.height to the same value, RenderStyle::setHeight still triggers access() which clones StyleBoxData, thus making future calls to RenderStyle::diff slower, since the pointer comparison fails.

Probably true of most of the DataRef<> types.
Comment 1 Simon Fraser (smfr) 2018-09-29 11:54:49 PDT 
Seen in MotionMark leaves test.
Comment 2 Simon Fraser (smfr) 2018-09-29 16:05:06 PDT 
Actually SET_VAR() already does a compareEqual(), so we're good.