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What were you doing?

Please tell us what site you were on, and what steps led to the error you are reporting

1. Open the Multiprocess Browser Toolbox
2. Go to settings.

What happened?

The new performance panel is disabled. Enabling it and restarting doesn't work either (the setting is lost).

This is important because the browser toolbox is the only thing that other apps (e.g., Thunderbird) have.

What should have happened?

At the very least it should probably be enabled / share the same defaults as the regular devtools. Ideally the devtools settings would match those of the profile that opened them, but maybe that's too much work.

I tried to move the new-performance-panel pref from firefox.js to all.js but that didn't make a difference.

Ah, https://searchfox.org/mozilla-central/source/devtools/client/definitions.js#285-289 probably explains this, fun...

Hey Emilio!

Indeed we disabled the new profiler from the Remote Toolbox because we thought that the Remote Toolbox skews profiling results too much.
We thought that the thunderbird use case would be fulfilled with Remote Profiling feature (ie: profiling from Firefox in a Remote Debugging session). Do you see a reason that this wouldn't work?

If this isn't convenient enough, we could try to bring the profiler UI (popup, about:profiling.) to thunderbird, but please remember that in the process of capturing a profile we need to open a webpage to profiler.firefox.com, which goes along some internal firefox code to support this as well as symbolication. IMO this looks more complex.

Thanks for your feedback!

(In reply to Julien Wajsberg [:julienw] from comment #2)

If this isn't convenient enough, we could try to bring the profiler UI (popup, about:profiling.) to thunderbird, but please remember that in the process of capturing a profile we need to open a webpage to profiler.firefox.com, which goes along some internal firefox code to support this as well as symbolication. IMO this looks more complex.

I'd definitely like the profiler UI in Thunderbird. Thunderbird can open web pages in its own tabs, so I suspect that wouldn't be too difficult depending on the FF code.

Are there docs about how to do something like that? I don't see an easy way to connect to TB from about:debugging

(In reply to Emilio Cobos Álvarez (:emilio) from comment #4)

Are there docs about how to do something like that? I don't see an easy way to connect to TB from about:debugging

It looks like that running thunderbird with thunderbird --start-debugger-server starts a debugger server on port 6000, that you can then connect to from about:debugging.

The MDN page in https://developer.mozilla.org/en-US/docs/Tools/Remote_Debugging/Thunderbird looks obsolete :/ Indeed I don't see this option in the Tools menu anymore, was that removed recently?

(In reply to Mark Banner (:standard8) from comment #3)

(In reply to Julien Wajsberg [:julienw] from comment #2)

If this isn't convenient enough, we could try to bring the profiler UI (popup, about:profiling.) to thunderbird, but please remember that in the process of capturing a profile we need to open a webpage to profiler.firefox.com, which goes along some internal firefox code to support this as well as symbolication. IMO this looks more complex.

I'd definitely like the profiler UI in Thunderbird. Thunderbird can open web pages in its own tabs, so I suspect that wouldn't be too difficult depending on the FF code.

I understand, we'd gladly give pointers to folks who'd like to implement this, as well as look at patches. But we (the profiler team) won't likely do all of it themselves as we're already spreading very thin. Moreover we don't have experience in Thunderbird development.

I've just filed bug 1747080 on adding the separate profile button.

Julien, the new Performance panel is now enabled in Browser Toolbox.
Should we close this bug?

(In reply to Jan Honza Odvarko [:Honza] (always need-info? me) from comment #7)

Julien, the new Performance panel is now enabled in Browser Toolbox.

TBH I'm kind of surprised that this is enabled in the browser toolbox generally. Do you know where that was done?
IIUC the browser toolbox comes with a lot of overhead and therefore I'm concerned about the usefulness of profiles gathered this way.

Should we close this bug?

I believe we can close this bug, yes.

Alex, just to double check, can you please provide quick summary of how the Performance panel works for BT?

(In reply to Jan Honza Odvarko [:Honza] (always need-info? me) from comment #9)

Alex, just to double check, can you please provide quick summary of how the Performance panel works for BT?

The perf panel has been enabled in the BT mostly for the BT itself so that when you open a second BT, which would debug the first, you will have the perf panel and be able to record profiles for the BT. This was added in bug 1764505. I had a patch in that bug to only show the perf panel in the second BT, but that was a bit complex both in UX and implementation.

There is a nice summary about the overall support of the perf-panel-in-toolbox over here:
https://searchfox.org/mozilla-central/rev/dd216c1307a2bf1b0d2465b9749fa86dac44303a/devtools/client/definitions.js#277-283