1669669 - Arenas containing only permanent things don't need to be swept

Status: RESOLVED FIXED

(Core :: JavaScript: GC, enhancement, P3)

Description

[Jon Coppeard (:jonco)]

Currently we allocate a lot of permanent atoms during startup (static strings and permanent atoms) and also JIT stubs. We always trace these at the start of a GC if we're collecting the atoms zone (in GCRuntime::traceRuntimeAtoms), therefore we don't need to sweep them since we know they will always survive.

It should be possible to move arenas containing only permanent things out of the main arena lists so that we can avoid sweeping them (until shutdown).

As a followup it should be possible to avoid tracing anything in these arenas too. Finally, it would be great if we could apply the same approach to the browser's permanent atoms.

Comment 1

[Jon Coppeard (:jonco)]

(In reply to Jon Coppeard (:jonco) from comment #0)

As a followup it should be possible to avoid tracing anything in these arenas too.

We should be able to get to the stage where all permanent things shared between runtimes are always marked. Then we could remove some of the checks for permanent things in marking, since they would be subsumed by the 'is marked' check.

Comment 2

[Jon Coppeard (:jonco)]

Currently there are only 4 JIT stubs in the atoms zone so it's not worth including them in this.

Comment 3

[Jon Coppeard (:jonco)]

Attachment: Bug 1669669 - Tidy GCRuntime to separate method and field definitions r?sfink

Comment 4

[Jon Coppeard (:jonco)]

Attachment: Bug 1669669 - Don't mark or sweep permanent atoms r?sfink

Depends on D121391

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b91ad7d1d7c0
Tidy GCRuntime to separate method and field definitions r=sfink
https://hg.mozilla.org/integration/autoland/rev/d3e0ca7e2145
Don't mark or sweep permanent atoms r=sfink

Comment 6

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/b91ad7d1d7c0
https://hg.mozilla.org/mozilla-central/rev/d3e0ca7e2145