Bug 75069 – Make elements with attributes smaller by eliminating the m_element back pointer in NamedNodeMap

• Component: DOM
• Status: RESOLVED FIXED

[Darin Adler]

The back pointer from the heap-allocated vector of attributes to the element is a waste of space. We should move the data from the current NamedNodeMap class into a new heap-allocated class that is independent of the DOM.

The NamedNodeMap class should then just be a class with an Element* in it. The pointer to NamedNodeMap could go into ElementRareData or some other map, and all the operations could be done based on data stored in the element and its data structures. NamedNodeMap would no longer have any data of its own.

[Caio Marcelo de Oliveira Filho]

I intend to implement this in steps. The first one is bug 77233 which would add ElementAttributeData, that will be the internal attribute storage. In that patch it is still part of NamedNodeMap, so no real change happen yet. It already contains the style related members that were in NamedNodeMap.

The next step is moving m_attributes to the ElementAttributeData, and the last step would be moving ElementAttributeData to Element and moving NamedNodeMap inside ElementRareData.

[Caio Marcelo de Oliveira Filho]

Created attachment 130754 [details]
Patch

[Caio Marcelo de Oliveira Filho]

It took more steps than planned because I made them smaller. In the end this made things easier to review. Tomorrow I'm planning to improve the ChangeLog with some empirical data of memory usage.

[Ryosuke Niwa]

Comment on attachment 130754 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=130754&action=review

> Source/WebCore/dom/Element.cpp:203
> +NamedNodeMap* Element::attributes() const

I don't think this function should have const qualifier.

[WebKit Review Bot]

Comment on attachment 130754 [details]
Patch

Attachment 130754 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/11861141

[Caio Marcelo de Oliveira Filho]

Created attachment 130810 [details]
Patch

[Caio Marcelo de Oliveira Filho]

Comment on attachment 130754 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=130754&action=review

>> Source/WebCore/dom/Element.cpp:203
>> +NamedNodeMap* Element::attributes() const
> 
> I don't think this function should have const qualifier.

What about Node::attributes()?

[Caio Marcelo de Oliveira Filho]

Committed r110172: <http://trac.webkit.org/changeset/110172>

[Julien Chaffraix]

Comment on attachment 130810 [details]
Patch

Clearing review flag from an old attachment so that it doesn't show on the review queue.

[Lucas Forschler]

Mass moving XML DOM bugs to the "DOM" Component.