Issue 2387 in v8: Parser/tiny-innerHTML is spending 17.5% of time in sem_post under v8?

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Status: New
Owner: ----

New issue 2387 by esei...@chromium.org: Parser/tiny-innerHTML is spending
17.5% of time in sem_post under v8?
http://code.google.com/p/v8/issues/detail?id=2387

Parser/tiny-innerHTML is spending 17.5% of time in sem_post under v8?

Tools/Scripts/run-perf-tests Parser/tiny-innerHTML.html
or directly:
http://trac.webkit.org/browser/trunk/PerformanceTests/Parser/tiny-innerHTML.html

first 10 lines from pprof --text output:

Running Parser/tiny-innerHTML.html (10 of 12)
363 17.5% 17.5% 363 17.5% sem_post
45 2.2% 19.7% 186 9.0% WebCore::HTMLTokenizer::nextToken
43 2.1% 21.7% 43 2.1% MaskPtr (inline)
34 1.6% 23.4% 34 1.6% append (inline)
32 1.5% 24.9% 66 3.2%
WebCore::SegmentedString::advanceAndUpdateLineNumber
30 1.4% 26.3% 695 33.5%
WebCore::HTMLDocumentParser::pumpTokenizer
29 1.4% 27.7% 34 1.6%
WebCore::SegmentedString::advanceAndUpdateLineNumber (inline)
27 1.3% 29.0% 65 3.1% tcmalloc::FL_Next
25 1.2% 30.3% 36 1.7%
WebCore::HTMLConstructionSite::reconstructTheActiveFormattingElements
23 1.1% 31.4% 45 2.2% SegmentedString (inline)

(The sample was generated by using the run-perf-tests --profile patch,
currently attached to https://bugs.webkit.org/show_bug.cgi?id=99517.)

I suspect we may be tickling some pathological case in v8, but I don't yet
know how to get v8 symbols to see.

[codesite...@google.com]

Comment #1 on issue 2387 by esei...@chromium.org: Parser/tiny-innerHTML is

spending 17.5% of time in sem_post under v8?
http://code.google.com/p/v8/issues/detail?id=2387

(No comment was entered for this change.)

Attachments:
pprof9657.0.svg 104 KB

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Comment #2 on issue 2387 by will...@chromium.org: Parser/tiny-innerHTML is

spending 17.5% of time in sem_post under v8?
http://code.google.com/p/v8/issues/detail?id=2387

I looked at the svg output. There are around 2064 samples in this svg
output (out of the nearly 2100, so there's some slop in other non-core
areas, but that's not worth examining). When we go from the WebCore
callback into V8, we still have all 2064 samples, so that part's cheap. By
the time we exit V8 into WebCore, we're at 1554 samples. Out of the 510
samples we spent in V8, there's a big chunk of that (360 samples) in
sem_post. The rest of the 1554 samples is distributed through WebCore, and
looks to primarily be in tokenizing.

[codesite...@google.com]

Updates:
Status: PendingFurtherInfo
Cc: dsl...@chromium.org

Comment #3 on issue 2387 by dsl...@chromium.org: Parser/tiny-innerHTML is

spending 17.5% of time in sem_post under v8?

https://code.google.com/p/v8/issues/detail?id=2387

Seems no longer relevant

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