Performance: Optimize Dromaeo/dom-query.html by caching NodeRareData on Document
https://bugs.webkit.org/show_bug.cgi?id=90059
Reviewed by Ryosuke Niwa.
This patch improves performance of document.getElementsBy*().
e.g. the patch makes Dromaeo/dom-query.html 5.4% faster.
Dromaeo/dom-query.html without the patch (Chromium/Linux):
784714 runs/s, 765947 runs/s, 803109 runs/s, 804450 runs/s
Dromaeo/dom-query.html with the patch (Chromium/Linux):
839245 runs/s, 829867 runs/s, 811032 runs/s, 847486 runs/s
Based on the assumption that document.getElementsByClassName(),
document.getElementsByTagName() and document.getElementsByName()
would be used frequently in the real world, this patch implements
a fast path for Document methods that require to access NodeRareData.
Specifically, this patch caches a pointer to NodeRareData on Document,
by which Document can access NodeRareData without looking up a HashMap.
The only performance concern is the overhead of the isDocumentNode() check
that this patch added to Node::ensureRareData. However, I could not
observe any performance regression caused by the overhead.
No tests. No change in behavior.
* dom/Document.cpp:
(WebCore::Document::Document):
(WebCore::Document::setCachedRareData): I didn't inline this method,
since the inlining slightly regressed performance for some reason.
(WebCore):
* dom/Document.h:
(WebCore):
(WebCore::Document::cachedRareData):
(Document):
(~Document): Moved 'm_document = 0' to the tail of the destructor,
since isDocumentNode() has to return true in clearRareData() that is called
in ~Document().
* dom/Node.cpp:
(WebCore::Node::ensureRareData):
(~Node): Moved the assertion into clearRareData().
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121412 268f45cc-cd09-0410-ab3c-d52691b4dbfc
4 files changed
