672439 - Avoid duplicate names for system compartment reporters

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Nicholas Nethercote [inactive]]

It's possible to have many compartments with the same codebase, and these all get lumped together in about:memory.  This is particularly bad if you have a Jetpack-based add-on, because you can have dozens of compartments merged under the name "[System Principal]".  It's misleading to lump them all together, we should separate them.

The very simplest thing we could do is add the compartment's address as a suffix to its name.  That'll give the required separation without giving any indication of where each duplicate compartment came from.  Maybe we can do better, eg. indicate which system-principal compartments are sandboxes.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: sample output

Here's the output of about:memory upon start-up with Bugzilla Tweaks installed, with the soon-to-be-attached patch applied.

Comment 2

[Nicholas Nethercote [inactive]]

Attachment: patch

This patch adds the address of a compartment, but only does it for system compartments, because (a) they're the only ones we're seeing lots of compartments with the same name, and (b) the addresses are a bit ugly, so we shouldn't show them where they're not useful.

An example:

│  ├──14.04 MB (20.68%) -- compartment([System Principal], 0x7ffb8c6a5000)
│  │  ├───9.20 MB (13.56%) -- gc-heap
│  │  │   ├──4.59 MB (06.76%) -- objects
│  │  │   ├──2.15 MB (03.17%) -- shapes
│  │  │   ├──1.70 MB (02.51%) -- strings
│  │  │   ├──0.56 MB (00.82%) -- arena-unused
│  │  │   └──0.20 MB (00.29%) -- (3 omitted)
│  │  ├───2.02 MB (02.97%) -- scripts
│  │  ├───0.97 MB (01.43%) -- string-chars
│  │  ├───0.81 MB (01.20%) -- mjit-code
│  │  ├───0.58 MB (00.85%) -- (3 omitted)
│  │  └───0.46 MB (00.68%) -- object-slots

And see the attachment for more examples.

Comment 3

[Andreas Gal :gal]

Comment on attachment 546715 [details] [diff] [review]
patch

There is a special place reserved in hell for people who do hard-coding like this. Just say'n.

Comment 4

[Nicholas Nethercote [inactive]]

Which hard-coding?  I'm not relying on the name of the system principal, I'm using JSCompartment::isSystemCompartment.  Indeed, the patch removes one place where the name was hard-coded, using SYSTEM_PRINCIPAL_SPEC instead.

Comment 5

[Andreas Gal :gal]

Yeah, the original sin was done by gregor. We will try to add some clean API any-time-now (tm).

Comment 6

[Nicholas Nethercote [inactive]]

Gregor's hack was fixed by bug 671482.  Bug 669123 is still open for a more general partitioning of compartments, should we desire it.

Comment 7

[Nicholas Nethercote [inactive]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/877914fc95bb

Comment 8

[Marco Bonardo [:mak]]

http://hg.mozilla.org/mozilla-central/rev/877914fc95bb