1313373 - Improve JSON::stringify peformance for kraken-stringify-tinderbox

Status: NEW

(Core :: JavaScript Engine, defect, P3)

Description

[Hannes Verschore [:h4writer]]

We are quite slow on https://arewefastyet.com/#machine=29&view=single&suite=kraken&subtest=stringify-tinderbox . Looking into it this is mostly JSON::stringify performance.

It might be good to look into the benchmark and see where we spend our time. And try to decrease the time spend in that function.

The benchmark is located:
https://github.com/h4writer/arewefastyet/tree/master/benchmarks/kraken/tests/kraken-1.1

The stringify function is located:
http://searchfox.org/mozilla-central/source/js/src/json.cpp#596

After compiling a shell you can run the specific test like:
$ $JS/dist/bin/js -f json-stringify-tinderbox-data.js -e "var start = new Date();" -f json-stringify-tinderbox.js -e "print(new Date() - start)"

Comment 1

[André Bargull [:anba]]

We could easily gain a ~7% improvement when specializing the GetElement call in [1] for dense array elements (similar to [2]).

[1] https://dxr.mozilla.org/mozilla-central/rev/3f4c3a3cabaf94958834d3a8935adfb4a887942d/js/src/json.cpp#500
[2] https://dxr.mozilla.org/mozilla-central/rev/3f4c3a3cabaf94958834d3a8935adfb4a887942d/js/src/jsarray.cpp#257-263

Comment 2

[Jan de Mooij [:jandem]]

We landed some patches for this last week. We're still a bit slower, I can probably get back to this in a few weeks/months.