[Webkit-unassigned] [Bug 76003] REGRESSION (r104210): WebProcess spins at 100% CPU for several minutes when loading an internal Apple site

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=76003





--- Comment #2 from Ryosuke Niwa <rniwa at webkit.org>  2012-01-10 17:18:55 PST ---
(In reply to comment #0)
> After r104210 we're seeing WebProcess spin at 100% CPU for several minutes after loading pages on an internal Apple site. A sample shows that almost all of the time is being spent in DynamicSubtreeNodeList::length below calls to WebCore::JSNodeList::getOwnPropertySlotByIndex.  I'll attach a reduction that demonstrates the regression.

According to my research people rarely modified DOM while hanging onto node list. This regression is the most pathological case where you're looping over node list and modifying DOM.

I suppose such code wasn't as unusual as I initially thought but you can get the same hang even before r104210 if you had modified the class name of any element inside the loop; e.g. element.className = 'hide';

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