1780547 - Missing symbols/js function name in some profile records

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P3)

Description

[Alexandre Poirot [:ochameau]]

Recently, while profiling DevTools, I started seeing more and more profiles missing the function names.

This might be related to JIT as in the current profile I see js::jit::MaybeEnterJit before the frames missing proper naming.

This isn't so obvious to reproduce, but here is a reliable way for me to reproduce:

• Open the browser console,
• run for(let i=0; i<100000; i++) console.log({foo: i})
  This will freeze FX for a bit.
• Record a profile while closing the browser console.
  This will also freeze FX for even longer and you will see missing symbols in the profile record.

Here is an example of such record:
https://share.firefox.dev/3aPPr1b

Comment 1

[Matthew Gaudet (he/him) [:mgaudet]]

Lots of interesting nameless 'interpreter' frames.

Comment 2

[Jan de Mooij [:jandem]]

I'm pretty sure this is from the AutoSuppressProfilerSampling in Nursery::traceRoots. In this case we spend a lot of time under DebugAPI::traceAllForMovingGC.

@jonco: I think we could shorten the AutoSuppressProfilerSampling range a bit, especially if we make the MarkRuntime step the first one in traceRoots?

Comment 3

[Jon Coppeard (:jonco)]

I don't think we can make MarkRuntime the first step, but we can stop suppressing the sample during DebugAPI::traceAllForMovingGC.

Comment 4

[Jon Coppeard (:jonco)]

Attachment: Bug 1780547 - Reduce the length of time the gecko profiler is suppressed for while collecting the nursery r?jandem

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d6b88be6a858
Reduce the length of time the gecko profiler is suppressed for while collecting the nursery r=jandem

Comment 6

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/d6b88be6a858

Comment 7

[Jon Coppeard (:jonco)]

(In reply to Alexandre Poirot [:ochameau] from comment #0)
Alexandre, did this help at all?

Comment 8

[Alexandre Poirot [:ochameau]]

Yes, it seems to be fixed, using comment 0 STR I now get such profile:
https://share.firefox.dev/3bE7O9q

There is still one intermediate frame still being an address, but that doesn't prevent me from understanding what is happening.

Thanks a lot for jumping on this!

Comment 9

[Jon Coppeard (:jonco)]

(In reply to Alexandre Poirot [:ochameau] from comment #8)
No problem, glad this is working now.