937227 - fix uninitialized event-* stats in about:memory

Status: RESOLVED FIXED

(Toolkit :: about:memory, defect)

Description

[Nathan Froyd [:froydnj]]

On a freshly started browser, about:memory is showing me things like:

1,115,980,845,296 (100.0%) -- event-counts
├──1,111,801,141,061 (99.63%) -- window-objects
│  ├────929,984,040,527 (83.33%) -- (217 tiny)
│  │    ├────8,359,410,760 (00.75%) -- top(chrome://browser/content/browser.xul, id=3)/active
│  │    │    ├──4,179,707,243 (00.37%) -- window(chrome://browser/content/browser.xul)/dom
│  │    │    │  ├──4,179,629,073 (00.37%) ── event-targets [2]
│  │    │    │  └─────────78,170 (00.00%) ── event-listeners [2]
│  │    │    └──4,179,703,517 (00.37%) -- window(about:blank)/dom
│  │    │       ├──4,179,629,068 (00.37%) ── event-targets [2]
│  │    │       └─────────74,449 (00.00%) ── event-listeners [2]
│  │    ├────8,359,409,291 (00.75%) ++ top(chrome://browser/content/browser.xul, id=15)/active
│  │    ├────8,359,406,425 (00.75%) ++ top(chrome://browser/content/browser.xul, id=17)/active
│  │    ├────8,359,405,569 (00.75%) ++ top(chrome://browser/content/browser.xul, id=13)/active
│  │    ├────8,359,392,706 (00.75%) ++ top(https://bugzilla.mozilla.org/show_bug.cgi?id=904336, id=403)/active
│  │    ├────6,269,558,208 (00.56%) ++ top(about:newtab, id=660)/active
│  │    ├────4,179,711,542 (00.37%) ++ top(https://mail.mozilla.com/zimbra/#1, id=275)/active/window(https://mail.mozilla.com/zimbra/#1)/dom
│  │    ├────4,179,709,343 (00.37%) ++ top(about:blank, id=377)/active/window(about:blank)/dom
│  │    ├────4,179,709,339 (00.37%) ++ top(about:blank, id=55)/active/window(about:blank)/dom

which seems totally bogus.  Unless I misunderstand, we are not properly initializing the counts for those stats in nsWindowSizes.  Patch in a moment.

Comment 1

[Nathan Froyd [:froydnj]]

Attachment: zero-initialize fields in nsWindowSizes

Boy, it sure would be nice if valgrind tests were working! ;)

Comment 2

[Nicholas Nethercote [inactive]]

Argh.  It looks like this was never working correctly.  It's frustrating that these are not sizes and so don't fit nicely into the FOR_EACH_SIZE macro.

Can you please nominate for Aurora backporting once it's landed?

Comment 3

[Nathan Froyd [:froydnj]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/a00f18602394

Comment 4

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Aha, I was wondering what was causing this, but hadn't gotten around to looking into it.

froydnj++

Comment 5

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/a00f18602394

Comment 6

[Nathan Froyd [:froydnj]]

Comment on attachment 830330 [details] [diff] [review]
zero-initialize fields in nsWindowSizes

[Approval Request Comment]
Would like to uplift this so that about:memory works better in Aurora.

Bug caused by (feature/regressing bug #): bug 904720
User impact if declined: The handful of people who look at about:memory will be less confused.
Testing completed (on m-c, etc.): On m-c.
Risk to taking this patch (and alternatives if risky): None.
String or IDL/UUID changes made by this patch: None.

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/6c7eb9d6e528