RESOLVED WONTFIX 116933
getData16SlowCase shows up on Mobile Gmail profile 
https://bugs.webkit.org/show_bug.cgi?id=116933
Summary getData16SlowCase shows up on Mobile Gmail profile
Ryosuke Niwa
Reported 2013-05-29 01:07:15 PDT
Consider merging https://chromium.googlesource.com/chromium/blink/+/0d0e52b5e2d15baadb7703028e83e6736751830b When loading Mobile Gmail in content_shell, StringImpl::getData16SlowCase shows up as 0.35% of the total profile. We're hitting this code path because the HTML parser causes *all* character tokens to (temporarily) have 16 string buffers because ExternalCharacterTokenBuffer operates in terms of UChar*, which assumes a 16 bit string buffer. This CL changes CharacterTokenBuffer to operate in terms of offsets into Strings, which is agnostic as to the backing buffer for the String. As a result, we can often just use the HTMLTokenizer-generated String in the DOM directly. After this CL, getData16SlowCase doesn't show up on the profile at all.
Attachments
Work in progress (10.69 KB, patch)
2013-05-29 21:51 PDT, Ryosuke Niwa 		no flags
DetailsFormatted DiffDiff
A/B test results of variants of the patch (39.22 KB, text/html)
2013-05-29 21:51 PDT, Ryosuke Niwa 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Darin Adler
Comment 1 2013-05-29 12:27:00 PDT
Sounds like a really good optimization. We should get that one in.
Adam Barth
Comment 2 2013-05-29 18:38:02 PDT
It's less of a big deal for the main thread parser, but probably worth merging in any case.
Ryosuke Niwa
Comment 3 2013-05-29 21:51:19 PDT
Created attachment 203308 [details] Work in progress
Ryosuke Niwa
Comment 4 2013-05-29 21:51:58 PDT
Created attachment 203309 [details] A/B test results of variants of the patch
Ryosuke Niwa
Comment 5 2013-05-29 21:53:57 PDT
I've made many variants of this patch but all of them had a net negative impact on the performance at least on html-parser.html.
Adam Barth
Comment 6 2013-05-29 22:56:10 PDT
Did you test it with the threaded parser?
Ryosuke Niwa
Comment 7 2013-05-29 22:57:39 PDT
(In reply to comment #6) > Did you test it with the threaded parser? No. It's conceivable that this is a performance gain with the threaded parser.
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