636558 - Reduce OffTheBooks allocation to (nearly) zero.

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine, defect)

Description

[Paul Biggar]

After bug 634155, there will be 42 OffTheBooks allocations. The GC does not know about these allocations, and so is unable to factor them into its decisions. We should remove these wherever possible.

Comment 1

[Andreas Gal :gal]

There is actually a ton more of these places, literally thousands--outside the JS engine. I think the right thing to do here is to start monitoring overall process memory use.

Comment 2

[Paul Biggar]

(In reply to comment #1)
> There is actually a ton more of these places, literally thousands

I don't understand. I thought allocating JS objects etc went through the JSAPI, like using JS_NewObject.

Comment 3

[Andreas Gal :gal]

Yes, JS object headers are allocate inside the engine. The embedding can attach megabytes of malloc-ed memory to a JS object though. The JS heap is usually a small part of our total memory profile.

Comment 4

[Brendan Eich [:brendan]]

Also, unless the GC incremental rewrite that is ongoing has changed things, the when-to-GC heuristics are touchy and adding more on-the-books accounting can cause SS and other benchmark regressions due to too much GC.

/be

Comment 5

[Brendan Eich [:brendan]]

So, retuning will be a wild ride. Definitely do not want for Fx4.

Comment 1 is right and there's even some electrolysis work to build on, IIRC. Cc'ing cjones.

/be

Comment 6

[Nicholas Nethercote [inactive]]

(In reply to comment #1)
> There is actually a ton more of these places, literally thousands--outside the
> JS engine. I think the right thing to do here is to start monitoring overall
> process memory use.

Does this mean adding OffTheBooks was a waste of time?

Comment 7

[Andreas Gal :gal]

No, it means it needs more work.