757483 - Score Rush gets more choppy w/ igc

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Luke Wagner [:luke]]

Attachment: incremental GC profile

With bug 750834 Score Rush is pretty smooth (17ms to render a frame).  The GC pauses are 35ms which is also pretty ok.  However, if you turn on igc, things are observably worse.

The per-frame profile attached also looks a lot worse: lots of recompilation, lots of interpreter time.  It almost looks like there is a bug involving igc where we throw away/recompile too much.

(To view the profile, you'll need to use billm's viewer.)

Comment 1

[Luke Wagner [:luke]]

Attachment: non-incremental GC profile

This is w/ igc turned off.  Looks much prettier.

Comment 2

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

Attachment: patch

We were setting the preserve flag in BeginMarkPhase, which is called once per incremental GC, and then unsetting it in ~AutoGCSession, which is called at the end of every slice. So in later slices, code was getting thrown away.

Comment 3

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

https://hg.mozilla.org/integration/mozilla-inbound/rev/9ddbd1da2f9b

Comment 4

[Luke Wagner [:luke]]

Wow, that was fast!  With this patch, I can see the biggest GC slice (the first) is only 16.6ms and the whole frame renders in 28.4ms; big improvement over non-incremental.

Comment 5

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/9ddbd1da2f9b