Bug 75315 – Reduce memory used by SpaceSplitString.

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

[Andreas Kling]

WebCore/dom/SpaceSplitString, used primarily for element class names, is quite wasteful memory wise. We could get massive gains with some simple trickery..

[Andreas Kling]

Created attachment 120679 [details]
Proposed patch

[Sam Weinig]

Comment on attachment 120679 [details]
Proposed patch

View in context: https://bugs.webkit.org/attachment.cgi?id=120679&action=review

> Source/WebCore/dom/SpaceSplitString.h:75
> +            Vector<AtomicString>* m_vector;

This Vector used to have an inline capacity of 8, which I remember being a speedup at one point.

[Andreas Kling]

I instrumented the Alexa top sites to find out how many substrings we normally find in the class attribute, here are the results (number of substrings: percentage of class attributes):

1: 64.20%
2: 25.64%
3: 6.15%
4: 2.28%
5: 0.95%
6: 0.35%
7: 0.21%
8: 0.13%
9: 0.06%
10: 0.08%
11: 0.03%
12: 0.01%

Given this data, I think we can reduce the inline capacity down to 2 where we'd save good amounts of memory and still cover 90% of cases.

[Andreas Kling]

Created attachment 120705 [details]
Proposed patch v2

[Sam Weinig]

Comment on attachment 120705 [details]
Proposed patch v2

I like it.

[WebKit Review Bot]

Comment on attachment 120705 [details]
Proposed patch v2

Attachment 120705 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/10993749

New failing tests:
http/tests/inspector/resource-tree/resource-tree-document-url.html

[Andreas Kling]

Comment on attachment 120705 [details]
Proposed patch v2

Clearing flags on attachment: 120705

Committed r103790: <http://trac.webkit.org/changeset/103790>

[Andreas Kling]

All reviewed patches have been landed.  Closing bug.