663920 - Cycle collector telemetry: num of RCed and GCed nodes in graph, num of objects collected

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[(dormant account)]

Attachment: telemetry

Andrew added a few extra stats to diagnose cycle collector issues.

Comment 1

[(dormant account)]

Comment on attachment 538973 [details] [diff] [review]
telemetry

This is Andrew's patch, I just updated the telemetry probes

Comment 2

[Andrew McCreight [:mccr8]]

Another thing we could think about tracking is the number of edges.  This could be done fairly efficiently (if approximately) by tracking the number of blocks allocated for edges.  However, the number of nodes is probably a decent proxy for the number of edges.

Comment 3

[(dormant account)]

Attachment: telemetry

Sorry, forgot to qref the previous patch

Comment 4

[Andrew McCreight [:mccr8]]

Attachment: add telemetry for the num of RCed and GCed nodes visited by the CC, and how many were collected

Unbitrotted the previous patch, and did a little bit of cleanup to make the naming consistent.  I also added telemetry for the number of nodes we collected, which was easy because the CC already tracks that number.

Comment 5

[Ben Turner (not reading bugmail, use the needinfo flag!)]

Comment on attachment 543470 [details] [diff] [review]
add telemetry for the num of RCed and GCed nodes visited by the CC, and how many were collected

Review of attachment 543470 [details] [diff] [review]:
-----------------------------------------------------------------

::: xpcom/base/nsCycleCollector.cpp
@@ +1021,5 @@
>  
>      nsPurpleBuffer mPurpleBuf;
>  
> +    PRUint32 mVisitedRefCounted;
> +    PRUint32 mVisitedGCed;

Nit: Comment here that these are only used for telemetry tracking.

@@ +2205,5 @@
>      mPtrLog(nsnull)
>  #else
> +    mPurpleBuf(mParams),
> +    mVisitedRefCounted(0),
> +    mVisitedGCed(0)

Hm, you're not initializing these in the non-DEBUG_CC case. I'd move them before mPurpleBuf in the class decl as well as here so that you don't get affected by the #ifdef.

Comment 6

[Andrew McCreight [:mccr8]]

Attachment: add telemetry for the num of RCed and GCed nodes visited by the CC, and how many were collected

Addressed review comments.  Carrying forward bent's r+.

Comment 7

[Marco Bonardo [:mak]]

http://hg.mozilla.org/mozilla-central/rev/f89d4b284590

Comment 8

[Andrew McCreight [:mccr8]]

I've been keeping an eye on this on my own computer since it landed.  It mostly looks reasonable, but the buckets for the number of objects being collected will probably need to be adjusted.  There are buckets for 0, 2, 4, 8, 10, 13, 16, etc. with things in them that could probably be combined together more.  In addition, I already have one collection with 100k objects in it, which probably maxed it out.