731423 - GC: Don't do incremental GCs during V8

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Gregor Wagner [:gwagner]]

I see a regression on splay from Aurora to Nightly from about 8350 to 6950 on my MP.
The GC log shows that the GC pause time increased from around 40ms to 60ms because of reset GCs.

Comment 1

[David Mandelin [:dmandelin]]

Fixed for now by the disabling of IGC.

Comment 2

[Gregor Wagner [:gwagner]]

The current scores when I enable/disable IGC in a nightly:

disabled: around 7900
enabled: around 6600

Comment 3

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Attachment: patch

I wasn't able to reproduce the performance difference. However, we were running incremental GCs during V8, which could certainly affect performance. With this patch, all my GCs during V8 are non-incremental. It just ensures that if we hit the allocation trigger, we always do an incremental GC. We never really hit this during interactive apps, since they'll always go through the MaybeGC trigger first.

Comment 4

[Gregor Wagner [:gwagner]]

(In reply to Bill McCloskey (:billm) from comment #3)
> Created attachment 626583 [details] [diff] [review]
> patch
> 
> I wasn't able to reproduce the performance difference. However, we were
> running incremental GCs during V8, which could certainly affect performance.
> With this patch, all my GCs during V8 are non-incremental. It just ensures
> that if we hit the allocation trigger, we always do an incremental GC. We
> never really hit this during interactive apps, since they'll always go
> through the MaybeGC trigger first.

Yep the performance regression is gone even without this patch. Did some allocation trigger change within the last 3 weeks?
Anyways this patch also makes sense. Maybe you should change the the summary.

Comment 5

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/95e2e6a47831

I don't know what would have changed the score. A lot has been changing lately.

Comment 6

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/95e2e6a47831