1350612 - dbg.onNewGlobalObject can be too slow even when Debugger in NOT enabled

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, enhancement)

Description

[(no longer active)]

See this profile: https://perfht.ml/2nnVluw

In this profile, it's taking ~5ms every time we load a JSM in the parent process it seems.

Comment 1

[Patrick Brosset <:pbro>]

Hi Jim,
Do you mind taking a look at this please?

Comment 2

[Jim Blandy :jimb]

Does this problem occur when we are not using devtools on chrome code? Unless someone has the add-on debugger or the chrome debugger open, onNewGlobalObject should never be called at all.

Comment 3

[(no longer active)]

(In reply to Jim Blandy :jimb from comment #2)
> Does this problem occur when we are not using devtools on chrome code?

Yes.

> Unless someone has the add-on debugger or the chrome debugger open,
> onNewGlobalObject should never be called at all.

That was surprising to me as well...

Comment 4

[Jim Blandy :jimb]

Okay, well, that's probably the bug.

Comment 5

[Jim Blandy :jimb]

(I'm looking into this.)

Comment 6

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

(Assigning in response to comment 5.)

Comment 7

[Kannan Vijayan [:djvj]]

:jimb, do you have progress on this?

Comment 8

[Bryan Clark (DevTools PM) [:clarkbw]]

:jimb, checking in on this again.  Any progress to report here?

Comment 9

[Jim Blandy :jimb]

I'm sorry. No, I haven't been looking at this at all. I will put it atop my list. I should be able to look at it tomorrow.

Comment 10

[Jim Blandy :jimb]

I'm not able to see any calls to js::Debugger::fireNewGlobalObject or even Debugger::setOnNewGlobalObject. Ehsan, does it still show up in your profiles?

I'm putting calls to `abort` in those two functions in my daily use browser; we'll see how it goes.

Comment 11

[(no longer active)]

I haven't seen it, but I also haven't honestly been looking for it...  Although it is kind of odd that I haven't run into it in 4 months!

The abort calls should be quite conclusive at any rate.  If those lead nowhere, please don't burn more time on this, sorry this wasted much of your time, this bug was quite weird, I still don't understand what the profile in comment 0 shows.  :/

Comment 12

[Jim Blandy :jimb]

Yes, I've been running a Firefox that crashes promptly if I open the Browser console, so I think we can say that this path is no longer being reached.