638199 - Shrink ArenaHeader

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Gregor Wagner [:gwagner]]

We can move some fields from ArenaHeader to the debug mode.

Comment 1

[Gregor Wagner [:gwagner]]

Attachment: patch

Use thingSize and isUsed only in debug mode.

Comment 2

[Gregor Wagner [:gwagner]]

Attachment: patch

Comment 3

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

I'm actually not too familiar with the low-level arena code. A few questions:
- Why did you move the assertion in Arena<T>::mark?
- Why is it okay to get rid of the CGCT_FREEARENA check?
- In Chunk::init, it seems like you should be setting arena->compartment to NULL. Is it okay to assume that new chunks are zeroed?

Comment 4

[Gregor Wagner [:gwagner]]

(In reply to comment #3)
> I'm actually not too familiar with the low-level arena code. A few questions:
> - Why did you move the assertion in Arena<T>::mark?

Because I removed the redundant check in MarkIfGCThingWord. Now we can enter this function for an unsued arena and the thingsize is 0;
Only after "if (!aheader.compartment || inFreeList(alignedThing))" we know that the arena is used now.
 

> - Why is it okay to get rid of the CGCT_FREEARENA check?
It is redundant.

> - In Chunk::init, it seems like you should be setting arena->compartment to
> NULL. Is it okay to assume that new chunks are zeroed?

Good point! I think this line got lost during my last merge.

Comment 5

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

Comment on attachment 517320 [details] [diff] [review]
patch

OK, now I see. Thanks.

Comment 6

[Gregor Wagner [:gwagner]]

http://hg.mozilla.org/tracemonkey/rev/d339633d2c42

Comment 7

[Chris Leary [:cdleary] (not checking bugmail)]

http://hg.mozilla.org/mozilla-central/rev/d339633d2c42