593351 - pagemap code: over-conservatively alloc'd by one page/block?

Status: RESOLVED WONTFIX

(Tamarin Graveyard :: Garbage Collection (mmGC), defect)

Description

[Felix S. Klock II [:pnkfelix, :fklock]]

Investigations during Bug 581070 led Felix to believe that the code is unnecessarily adding 1 to its calculations of the number of pages to allocate.

It is not clear what the origin of the increment was.  Its possible it was (or still is) working around bugs elsewhere.

So it should be investigated.  At worst, it is allocating a bit more storage than we would like for the page map.  But before removing it to try to be more aggressive about memory consumption, I would want to see evidence that the test suite is exercising the boundary cases here; otherwise it is higher risk than I would like to just put it in.

Comment 1

[Tommy Reilly]

related? https://bugzilla.mozilla.org/show_bug.cgi?id=588079

Comment 2

[Felix S. Klock II [:pnkfelix, :fklock]]

(In reply to comment #1)
> related? https://bugzilla.mozilla.org/show_bug.cgi?id=588079

Maybe related.

I had originally hypothesized that the over-allocation by 1 was hiding the memEnd miscalculation described in bug 588079.  But as you have quite clearly demonstrated, even if it was masking the memEnd miscalculation in some cases, it was not covering all of them.

Comment 3

[Sylvestre Ledru [:Sylvestre]]

No assignee, updating the status.

Comment 4

[Sylvestre Ledru [:Sylvestre]]

No assignee, updating the status.

Comment 5

[Sylvestre Ledru [:Sylvestre]]

No assignee, updating the status.

Comment 6

[Sylvestre Ledru [:Sylvestre]]

No assignee, updating the status.

Comment 7

[Sylvestre Ledru [:Sylvestre]]

Tamarin isn't maintained anymore. WONTFIX remaining bugs.