843936 - [perf] reading element.offsetHeight and element.offsetWidth very extremely slow

Status: RESOLVED WORKSFORME

(Core :: Web Painting, defect, P3)

Description

[Honza Bambas (:mayhemer)]

This was also discovered while scrolling simile timeline (as bug 843935).  I am solving this issue by caching the value which makes scrolling visibly faster.

To compare, in Chrome (dev) moving the timeline is absolutely smooth.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Are you interleaving these gets with style changes?

Comment 2

[Honza Bambas (:mayhemer)]

(In reply to Boris Zbarsky (:bz) from comment #1)
> Are you interleaving these gets with style changes?

No idea, the timeline code is complex and I am not an author.

However, there is significant impact of caching the offset* values.  The timeline has a more smooth feeling and is objectively faster.  Unfortunately, only a bit faster...

Not cached code, timing of [1]:
Calls   %       Own Time        Time            Average         Min     Max
234	94.92%	3020.069ms	3020.646ms	12.909ms	0.009ms	36.798ms

Cached code of [1]:
Calls   %       Own Time        Time            Average         Min     Max
204	0.97%	1.314ms	        1.855ms	        0.009ms	        0.008ms	0.016ms


[1] http://code.google.com/p/simile-widgets/source/browse/timeline/trunk/src/webapp/api/scripts/band.js#351


PS: In general, using chrome and their profiler, they spend 95% of JS time at idle...

We use 100% of a CPU core time (with either the "caching patch" or w/o).  Chrome uses around 60% (rough est, since I'm on an 8 core machine).

Comment 3

[Timothy Nikkel (:tnikkel)]

Last comment almost a decade ago, a lot has changed since then. Testcase no longer seems accessible. If there is still a problem here we'll need updated STR and a testcase.