676939 - Reuse compiled scripts across pages

Status: RESOLVED DUPLICATE of bug 1670403

(Core :: JavaScript Engine, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

I was looking in about:memory and saw 13MB for mjit code for tbpl.mozilla.org. I expect this was because I had a lot of tbpl tabs open. It would be nice if these tabs could share what's likely the same mjit code.

I talked with shaver and he had some idea about how this might be possible.

Comment 1

[Luke Wagner [:luke]]

We share jitted code within a compartment so, assuming all your tbpl.mozilla.org tabs are being properly put in the same compartment (which it sounds like they are), then we should be reusing those compiled scripts.  A separate question is why tbpl generates 13MB of mjit code.

Comment 2

[Luke Wagner [:luke]]

Oh wait, I'm totally wrong.  Each of those pages will compile its own copy of the JSScript so while compartment-per-domain doesn't *prevent* sharing code, we aren't.

Comment 3

[Boris Zbarsky [:bzbarsky]]

So the biggest issue I ran into last time I looked at this stuff was COMPILE_N_GO...

Comment 4

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

I don't know much about this stuff. But if COMPILE_N_GO is an issue, then I assume the tabs have different global objects. And if that's the case, then pretty soon all these scripts will be in different compartments (when we have compartment-per-global). And that will make this a lot harder.

Comment 5

[Boris Zbarsky [:bzbarsky]]

Yes, the tabs very much have different global objects.

Comment 6

[Bryan Thrall [:bthrall]]

Sharing compiled scripts has become more complicated because of Electrolysis and Fission.

Current efforts revolve around sharing Stencils; see stencil-nav bug.