542035 - Some characteristic of my profile + Adblock Plus or Firebug cause noticeable GC delay

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, defect)

Description

[Daniel Einspanjer [:dre] [:deinspanjer]]

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6

I was testing out the spinning dial demo in a recent blog post from Alix.  I was surprised that he stated that he was seeing less than 30ms delay when I was seeing much more than that. 50ms to 100ms.

I saw in the comments that Firebug could slow it down even if not actively using it.  This profile is also one that I've been using for about 8 months all the way through 3.6 betas and it has more than a dozen add-ons, so I figured I should try it with a different profile.
I tried with my "testing" profile that is much lighter and infrequently used.  I found with that profile that having the Adblock Plus extension enabled resulted in double the GC time.

I next tested with a brand new profile.  Initially, on first run of the profile, I was seeing 17ms delay.  I installed ABP and restarted and it was still around 17ms to 20ms.  After a couple of restarts, it jumped up to 30ms where it has remained.

Please let me know what info I can collect for you regarding this.  I'm going to try doing a screencast showing some of the back and forth testing I've done so far in case my description doesn't make enough sense.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Do we have some way to collect gc data?  It might be that adblock is just allocating a bunch of objects that we then have to traverse....

Comment 2

[Daniel Einspanjer [:dre] [:deinspanjer]]

While playing with this canvas demo, I noticed that at times I can still get very heavy GC pauses with 4.0b5:
http://rawkes.com/blog/2010/09/07/recreating-googles-bouncing-balls-logo-in-html5-canvas

The original link in the URL field of this bug estimates my GC delay at around 150ms.

I'm going to try running spin control and getting a dump to see if it highlights anything useful.

Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b5) Gecko/20100101 Firefox/4.0b5

Comment 3

[Daniel Einspanjer [:dre] [:deinspanjer]]

Since Fx isn't beachballing, spincontrol isn't recording anything.
With my current average being 150ms, it isn't terrible, only noticeable.  When I was looking at the Google logo canvas demo, I saw several GC pauses over 1 second.

I'll try to narrow down anything more specific and put it here if I discover it.

Comment 4

[Wayne Mery (:wsmwk)]

deinspanjer, do you still see this?

Comment 5

[Daniel Einspanjer [:dre] [:deinspanjer]]

Nope, Running with the current nightlies, GC delay is minimal even with my same ancient profile.