[Webkit-unassigned] [Bug 30988] Attribute cache purged too eagerly

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=30988





--- Comment #1 from James Robinson <jamesr at chromium.org>  2009-10-31 21:39:27 PDT ---
Created an attachment (id=42268)
 --> (https://bugs.webkit.org/attachment.cgi?id=42268)
Test page to see behavior

Attached is a simple test page to try out.  There's three versions of the loop
- the naive solution from the bug report, a version that stores the 'length'
property in a javascript variable, and a version that copies the entire node
list into a javascript array before mutating values.  On a pretty recent WebKit
nightly in Safari on OS X I get these times:

time elapsed (naive) for 5000 was 1490 ms
time elapsed (naive) for 5000 was 1393 ms
time elapsed (cache length) for 5000 was 471 ms
time elapsed (cache length) for 5000 was 481 ms
time elapsed (cache array) for 5000 was 10 ms
time elapsed (cache array) for 5000 was 10 ms

On Firefox 3.5.4 on OS X I get these times:

time elapsed (naive) for 5000 was 82 ms
time elapsed (naive) for 5000 was 24 ms
time elapsed (cache length) for 5000 was 128 ms
time elapsed (cache length) for 5000 was 13 ms
time elapsed (cache array) for 5000 was 130 ms
time elapsed (cache array) for 5000 was 29 ms

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