1759173 - Add support for perf's jitdump format

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P3)

Description

[Jeff Muizelaar [:jrmuizel]]

V8 supports this (--perf-basic-prof, --perf-prof-unwinding-info etc.) and it would be useful for being able to profile natively with perf. It could also be useful for being able to compare profiles of JS in V8 vs Spidermonkey.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

The format is documented here: https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jitdump-specification.txt

Comment 2

[Nicolas B. Pierron [:nbp]]

For what is worth, we already have some perf instrumentation here:
https://searchfox.org/mozilla-central/rev/d4d7611ee4dd0003b492b865bc5988a4e6afc985/js/src/builtin/Profilers.cpp#464

Comment 3

[Denis Palmeiro [:denispal]]

I would definitely like to support this so we can get better visibility into which functions are behaving poorly versus chrome. Right now we can find the problematic function pretty easily in the gecko profiler, but it's hard to understand why it's behaving poorly. So, I don't mind taking this if nobody else is planning on working on it.

Comment 4

[Markus Stange [:mstange]]

(In reply to Nicolas B. Pierron [:nbp] from comment #2)

For what is worth, we already have some perf instrumentation here:

And more here: (requires building with --enable-perf and running with IONPERF=func/block)
https://searchfox.org/mozilla-central/rev/44527269dd96db7a3da81aafff33c84a031864c7/js/src/jit/PerfSpewer.cpp

This supports the old perf.map format, not the newer jitdump format. (some more notes here)

Comment 5

[Denis Palmeiro [:denispal]]

The existing support for perf symbol maps will be removed in favour of jitdump.

Comment 6

[Denis Palmeiro [:denispal]]

Attachment: Bug 1759173: Remove perf symbol maps and add Jitdump support for Ion, Baseline, and Inline Caches r=iain

Comment 7

[Denis Palmeiro [:denispal]]

Attachment: Bug 1759173: Add source and IR annotation support for Jitdump r=iain

Depends on D148035

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/abefa20046ff
Remove perf symbol maps and add Jitdump support for Ion, Baseline, and Inline Caches r=iain
https://hg.mozilla.org/integration/autoland/rev/ba893c6048b5
Add source and IR annotation support for Jitdump r=iain

Comment 9

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/abefa20046ff
https://hg.mozilla.org/mozilla-central/rev/ba893c6048b5

Comment 10

[Alex Finder]

== Change summary for alert #34478 (as of Tue, 14 Jun 2022 19:14:42 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
2%	buzzfeed PerceptualSpeedIndex	macosx1015-64-shippable-qr	fission warm webrender	269.75 -> 264.25

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=34478