[Webkit-unassigned] [Bug 109884] Add CSS Property tracking to FeatureObserver. Creates new histogram for CSS Property usage data.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=109884





--- Comment #33 from Kassy Coan <kassycoan at gmail.com>  2013-03-26 03:52:51 PST ---
(In reply to comment #32)
> (From update of attachment 194985 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=194985&action=review
> 
> The feature seems very low value for all the bloat it introduces.
> 
> > Source/WebCore/css/CSSParser.cpp:1827
> >  bool CSSParser::parseValue(CSSPropertyID propId, bool important)
> >  {
> > +    if (m_context.m_document)
> > +        FeatureObserver::observe(m_context.m_document.get(), propId);
> 
> parseValue functions are hot. Have you measured what this does to our performance?

Yes I have measured. FeatureObserver has 1 main loop that is most time consuming, and it is very minor.

Here are elapsed time over a few runs. In the worse case, it took 80 microseconds.

Elapsed Time: 0.000080 count: 105

Elapsed Time: 0.000031 count: 103

Elapsed Time: 0.000029 count: 95

Elapsed Time: 0.000031 count: 95

Elapsed Time: 0.000028 count: 94

(count meaning the number of CSS Properties used on that page)

I believe the if check here is unnecessary (see my previous comment for explanation of how the RefPtr works for my reasoning), but I added it is as per request of Ojan, and I have not heard back yet of if it's good to remove.

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