726252 - record number of XPConnect and purple roots in CC log

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Andrew McCreight [:mccr8]]

Attachment: CC graph roots

If we print out the number of XPC and purple roots in the CC graph, then we can use that information to figure out why things are being included in the graph.

I think we can just do this by adding a few fake nodes to the graph.  That shouldn't mess up earlier versions of my script, and will make it easy to support both old and new logs in my scripts going forward.

I've hacked up a test version of this.  In the attached PDF, purple nodes are from the purple buffer, and red nodes are XPConnect roots.

Comment 1

[Andrew McCreight [:mccr8]]

One trickiness here is that XPConnect roots are added first, so if one of them is also in the purple buffer, we won't be able to tell.

Another problem is that my current method for logging this is tied to the way we traverse the CC graph: add all roots, then traverse from the roots.  If we changes to be more DFS, then it won't work.  We could add a flag per-object to indicate it if is a root or not, or perhaps that is premature generalization.

Comment 2

[Andrew McCreight [:mccr8]]

Attachment: hacky patch

For general use, you probably don't want gAlwaysLogCCGraphs to be true, and CollectTimeDebug may or may not be useful.

Comment 3

[Andrew McCreight [:mccr8]]

Attachment: oops wrong patch

Comment 4

[Johnny Stenback (:jst)]

Looks like this landed?

Comment 5

[Andrew McCreight [:mccr8]]

No, I just used it as a prototype to figure out what we should remove from the purple buffer.  I'm not really sure what a nice way to do it is.

Comment 6

[Andrew McCreight [:mccr8]]

Attachment: write out number of roots to CC log

Unbitrotted this.  Patch requires slightly flipping a variable in my dotify script.

Comment 7

[Andrew McCreight [:mccr8]]

I'm not actively working on this. I haven't needed anything like this for a while.