[Webkit-unassigned] [Bug 106586] NodeRareData and NodeListsNodeData are never deleted until Node is deleted even if they're no longer used

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=106586





--- Comment #9 from Elliott Sprehn <esprehn at chromium.org>  2013-01-24 21:14:51 PST ---
(In reply to comment #8)
> (In reply to comment #7)
> > It appears that once you have rare data childNodes is noticeably faster, so dropping rare data when the last node list goes away will probably make repeated traversals of the DOM through childNodes slower. I also question the perf impact from adding all of these subobjects into rare data, or dropping them, since it means lots more little allocations.
> 
> Of course, it'll make things slower because it's a trade off between CPU and memory usage. But did you see any perf. regressions from https://bugs.webkit.org/show_bug.cgi?id=107074 ? If not, I highly doubt that deleting one more object will have a significant perf. impact. And 3% memory use reduction is quite significant.

Can you explain the 3% improvement? When I looked into this there were about 3000 elements in a large sized web app, if at most 10% have rare data and rare data is 160 bytes (that was months ago, it's smaller now) that's only 47KB. That seems a far cry from 3% of the memory usage of a typical web app.

Can you post some real numbers of rare data usage on pages and how much memory this really saves? It would make sense to instrument rare data usage before we start these kinds of optimizations.

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