Bug 28332 – REGRESSION: significant slowdown on Celtic Kane "AJAX declaration" subtest

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Maciej Stachowiak]

http://www.betanews.com/article/Safari-403-speed-gains-hobbled-by-unexplained-poor-AJAX-performance/1250108985

This page claims: "Specifically, a heat where Safari 4 build 530.19 was timed at 23 ms, for a score of 8.96(almost nine times faster than IE7 on Vista), yielded a time of 371 ms (0.56) for build 531.9.1."

We have confirmation of a serious regression on both Mac and Windows.

[Maciej Stachowiak]

<rdar://problem/7144974>

[Maciej Stachowiak]

Radar bug closed as duplicate of <rdar://problem/7141850>

[Oliver Hunt]

Created attachment 35189 [details]
First pass at fixing regression.

[Oliver Hunt]

I'd appreciate it if folk could have a look at this first iteration of a fix for this regression.  It's actually quite straight forward in the end, it's memory neutral (actually due to what happens currently it's probably a memory win in the effected cases), and is a 1% progression on V8.

There is some gnarlyness to it though -- it uses a const_cast to be able to create the necessary pair for the hash lookup which is safe, but really really icky; it also adds StructureTransitionTable functions to Structure.h to allow inlining, but having seen performance i may try making them non-inlined and see if it's survivable.

[Oliver Hunt]

Sigh, the info here was lost :-(

Bug fix (and a couple of followup patches) landed in r47601, 47604, and 47605