1740752 - Experiment with allocating the nursery in a contiguous region of address space

Status: ASSIGNED

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

Description

[Jon Coppeard (:jonco)]

Currently the nursery is made up a of series of chunks which are not contiguous in memory. Reserving address space ahead of time and using this to allocate nursery memory contiguously could be better for the following reasons:

• cheaper post barriers (which don't require loads from the chunk header)
• simplification of nursery code
• it's a prerequisite for pointer compression

Possible downsides are:

• increased use of address space (may negatively affect 32bit platforms)

Comment 1

[Jon Coppeard (:jonco)]

Attachment: WIP: Bug 1740752 - Part 1: Reserve a region of address space for the nursery

Comment 2

[Jon Coppeard (:jonco)]

Attachment: WIP: Bug 1740752 - Part 2: Remove use of chunks vector

Depends on D154366

Comment 3

[Jon Coppeard (:jonco)]

Attachment: WIP: Bug 1740752 - Part 3: Only reserve the space necessary to grow the nursery to its maximum size

Depends on D154367

Comment 4

[Jon Coppeard (:jonco)]

Attachment: WIP: Bug 1740752 - Part 4: Add option to not commit memory initially

Depends on D154369

Comment 5

[Jon Coppeard (:jonco)]

Attachment: WIP: Bug 1740752 - Part 5: Don't commit nursery pages initially

Depends on D154370