1998353 - Make html accel also do SIMD writes

Status: RESOLVED FIXED

(Core :: DOM: HTML Parser, enhancement)

Description

[Henri Sivonen (:hsivonen)]

The SIMD acceleration adding in bug 1499682 and follow-ups accelerates the read side of code that was previously structured (both in the parser and the serializer) to do by-code-unit reads to find a stretch of data to later copy in bulk. This makes sense on the assumption that writes using memcpy are so much faster than by-code-unit writes that it makes sense to re-reread the data.

With SIMD acceleration, we've already read the data into SIMD registers. We should consider doing SIMD writes from the same inner loop that does the SIMD reads, since that might now be faster than re-reading the data later for bulk writing.

Comment 1

[Jan Jaeschke [:jjaschke]]

Attachment: Bug 1998353 - Store SIMD strides directly into strBuf in the HTML tokenizer. r=hsivonen!

Copy comment and quoted attribute data from the SIMD registers into
strBuf, avoiding a separate memcpy. The final stride may write past
strBufLen; the existing capacity bound keeps those writes within the
allocation.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/4c2be1029aab
https://hg.mozilla.org/integration/autoland/rev/387083f11eef
Store SIMD strides directly into strBuf in the HTML tokenizer. r=hsivonen

Comment 3

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/387083f11eef

Comment 4

[Performance Sheriff Bot]

Perfherder has detected a browsertime performance change from push 387083f11eef89e98d79269e14408a532ccd6e91.

No action is required from the author; this comment is provided for informational purposes only.

Improvement	Test	Platform	Options	Absolute values [old vs new]	Performance Profiles
2%	speedometer3 TodoMVC-jQuery/total (doc)	macosx1500-aarch64-nightlyasrelease	fission webrender	62.27 ms -> 61.10 ms	Before/After
2%	speedometer3 TodoMVC-jQuery/total (doc)	macosx1500-aarch64-nightlyasrelease	fission no-nova webrender	62.30 ms -> 61.24 ms	Before/After
2%	speedometer3 TodoMVC-JavaScript-ES6-Webpack-Complex-DOM/total (doc)	macosx1500-aarch64-nightlyasrelease	fission webrender	21.71 ms -> 21.35 ms	Before/After

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Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.