[Webkit-unassigned] [Bug 13115] New: REGRESSION: 1000% performance regression in DOM access by index, which was already slow

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=13115

           Summary: REGRESSION: 1000% performance regression in DOM access
                    by index, which was already slow
           Product: WebKit
           Version: 522+ (nightly)
          Platform: Macintosh PowerPC
               URL: http://www.hixie.ch/tests/adhoc/perf/dom/artificial/core
                    /001.html
        OS/Version: Mac OS X 10.4
            Status: UNCONFIRMED
          Severity: Major
          Priority: P1
         Component: HTML DOM
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jon at jonshier.com


As of r20309, WebKit's performance on the index portion of Hixie's DOM
benchmark has regressed 1000%, from 1.4s to 14s (Quad G5, 10.4.9, 1GB RAM). I
believe the relevant part of the test is this:

function testIndex(div) {
     for (var i = 0; i < count; i += 1) {
       divs[i] = div.childNodes[count*2 - i*2 - 1];
     }
   }

In contrast Opera completes this part of the test in .09s and Firefox 2 in .4s. 

(Bizarrely, the first time I run the test in shipping Safari, it comes up at
around 1.5 seconds. Then, the second and third times, the time doubles (3.5s,
7s). Relaunching Safari starts the process again.)


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