1005442 - memory reporter diff gets confused by null principals

Status: RESOLVED FIXED

(Toolkit :: about:memory, defect)

Description

[Bobby Holley (:bholley)]

(Not sure which component this belongs to - njn, can you reclassify?)

I was getting very confused over a diff between two memory reports, because it showed this:

│   │  ├──3.61 MB (25.62%) ++ (226 tiny)
│   │  └──1.17 MB (08.31%) ++ compartment(moz-nullprincipal:{09969844-1311-494d-8b90-6a50783f523b}, XPConnect Compilation Compartment)

And I was very surprised that the Compilation Compartment grew by so much. As it turned out, when I expanded "tiny", I found:

-1.08 MB (-7.70%) ++ compartment(moz-nullprincipal:{72419579-0050-4249-9dcb-e4ab09a7f156}, XPConnect Compilation Compartment)

Which makes a lot more sense. But this was very confusing. Given that null principals are generated with a random UUID which varies between runs, maybe we should avoid including those in the memory report, at least in the case where the compartment also has a name?

Comment 1

[Nicholas Nethercote [inactive]]

The diff tool currently anonymizes certain random things such as addresses and PIDs. Would doing the same for UUIDs fix this problem?

Comment 2

[Andrew McCreight [:mccr8]]

Also, I think tiny shouldn't include large negative values.

Comment 3

[Bobby Holley (:bholley)]

(In reply to Nicholas Nethercote [:njn] from comment #1)
> The diff tool currently anonymizes certain random things such as addresses
> and PIDs. Would doing the same for UUIDs fix this problem?

Yeah. Though would that cause us to lose information about addons, which use UUIDs that are not randomized at runtime?

(In reply to Andrew McCreight [:mccr8] from comment #2)
> Also, I think tiny shouldn't include large negative values.


I agree.

Comment 4

[Andrew McCreight [:mccr8]]

I filed bug 1005489 for that.

Comment 5

[Nicholas Nethercote [inactive]]

Attachment: Strip moz-nullprincipal UUIDs when diffing memory reports

This patch strips the UUIDs just from null principals, thus avoiding add-on
UUIDs.

Comment 6

[Andrew McCreight [:mccr8]]

Comment on attachment 8422146 [details] [diff] [review]
Strip moz-nullprincipal UUIDs when diffing memory reports

Review of attachment 8422146 [details] [diff] [review]:
-----------------------------------------------------------------

woot

Comment 7

[Nicholas Nethercote [inactive]]

Well that was fast! :)

https://hg.mozilla.org/integration/mozilla-inbound/rev/83b7b82834f0

Comment 8

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/83b7b82834f0