On Sun, Aug 2, 2009 at 1:45 AM, Adam Barth<[email protected]> wrote: > On Sun, Aug 2, 2009 at 1:41 AM, Adam Barth<[email protected]> wrote: >> On Sun, Aug 2, 2009 at 1:13 AM, Darin Adler<[email protected]> wrote: >>> I noticed that many JavaScript binding implementations are now calling the >>> virtual function scriptExecutionContext on DOM nodes. This should never be >>> done! That's a virtual function, so it's not as fast as calling document(). >>> The virtual Node::scriptExecutionContext() function should be made private >>> so that we can catch at least some cases of this programming mistake at >>> compile time. >>> >>> When this change was made, this presumably slowed down DOM bindings, since >>> document() is an inline function that expands to a single memory read and >>> scriptExecutionContext() is a virtual function call. >>> >>> When was this done? Can the person who did it fix it? >> >> Do you mean the two calls to scriptExecutionContext() in >> JSNodeCustom.cpp? Those appear to have been added in >> http://trac.webkit.org/changeset/40675 by Sam Weinig (reviewed by >> Darin Adler). > > Actually, that change just moved code that was actually introduced in > http://trac.webkit.org/changeset/38063 by Alexey Proskuryakov > (reviewed by Darin Adler).
In any case: https://bugs.webkit.org/show_bug.cgi?id=27931 I'll have a patch shortly. Please let me know if there are other call sites you'd like changed. >> If you mean one of the other 36 occurrences of >> scriptExecutionContext, I'm not sure, but we can certainly track it >> down. >> >> Is there a benchmark that shows the performance issue? That will be >> helpful in making sure we've fixed the problem. >> >>> There are various techniques that can be used to fix this. >>> >>> One is to only call scriptExecutionContext in generic code, and use >>> functions named document() in less generic code that's working with a Node >>> rather than an EventTarget. >>> >>> Another is to break scriptExecutionContext into virtual and non-virtual >>> parts as we do with functions like Node::prefix and Node::virtualPrefix. >>> >>> -- Darin >>> >>> _______________________________________________ >>> webkit-dev mailing list >>> [email protected] >>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev >>> >> > _______________________________________________ webkit-dev mailing list [email protected] http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
