1068696 - Ensure memory for SharedArrayBuffer is properly tracked

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, defect)

Description

[Lars T Hansen [:lth]]

More an investigative item than a bug: I'm not sure if the memory for the SharedArrayBuffer is tracked by memory measurements, but it ought to be (somehow).

Comment 1

[Nicholas Nethercote [inactive]]

SharedArrayBufferObject::addSizeOfExcludingThis() exists, and is called appropriately from JSObject::addSizeOfExcludingThis().

It looks like this:

> /* static */ void
> SharedArrayBufferObject::addSizeOfExcludingThis(JSObject *obj, mozilla::MallocSizeOf mallocSizeOf,
>                                                 JS::ClassInfo *info)
> {
>     info->objectsNonHeapElementsMapped += obj->as<SharedArrayBufferObject>().byteLength();
> }   

If SharedArrayBufferObject only has a single buffer and it's always mmapped then I think we're ok. 

You should be able to confirm by running an example that uses a large SharedArrayBufferObject and then looking in about:memory -- just search for "SharedArrayBufferObject" (assuming you're on a Nightly build or similar).

Comment 2

[Lars T Hansen [:lth]]

(In reply to Nicholas Nethercote [:njn] from comment #1)
> 
> If SharedArrayBufferObject only has a single buffer and it's always mmapped
> then I think we're ok. 

It does.

> You should be able to confirm by running an example that uses a large
> SharedArrayBufferObject and then looking in about:memory -- just search for
> "SharedArrayBufferObject" (assuming you're on a Nightly build or similar).

I did, and it works.  Thanks.