742028 - On MacOS, RSS is much larger than explicit

Status: RESOLVED INCOMPLETE

(Core :: General, defect)

Description

[Justin Lebar (not reading bugmail)]

bz had the following numbers on his 10.6 machine:

1,356,769,377 B ── explicit
  940,710,232 B ── heap-allocated
1,072,316,416 B ── heap-committed
         12.27% ── heap-committed-fragmentation
    3,321,856 B ── heap-dirty
  271,441,040 B ── heap-unallocated
  394,264,576 B ── js-gc-heap
  113,790,976 B ── js-main-runtime-gc-heap-decommitted
1,694,748,672 B ── resident

Notice that RSS is 338mb higher than explicit.

It's expected that RSS will be higher than explicit, but the difference should be mainly code (and explicit gets an unfair increase from non-resident memory, mainly gc-heap-decommitted, that njn made me put in explicit).

Anyway, what I think might be happening is that malloc_double_purge isn't working properly.  It's supposed to decommit MADV_FREE'd pages when you view about:memory, but maybe it's not.

Comment 1

[Jet Villegas (inactive)]

P2 per Memshrink

Comment 2

[Justin Lebar (not reading bugmail)]

One way one could look into this is by running the vmmap command.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee didn't login in Bugzilla in the last 7 months, so the assignee is being reset.

Comment 4

[Andrew McCreight [:mccr8]]

I think closing ancient memory reporter issues is fine.