1778077 - Use calloc for non-Wasm SharedArrayRawBuffer

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[Jan de Mooij [:jandem]]

Bug 1777231 reports our mapped-buffer-limit causing problems when using SharedArrayBuffer in JS.

A lot of the fields in SharedArrayRawBuffer are Wasm-specific. The plan is to add a WasmSharedArrayRawBuffer that contains the Wasm-specific bits. We can then also use calloc for the non-Wasm buffers, similar to what we already do for non-shared array buffers.

This is faster and will use less memory when allocating (many) SABs from JS.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1778077 part 1 - Inline SharedArrayRawBuffer::AllocateInternal into the two callers. r?sfink!

This forks the non-Wasm and Wasm code paths, which will make it easier to simplify
the non-Wasm code in a later patch.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1778077 part 2 - Move dropReference call into dropRawBuffer. r?sfink!

This ensures the buffer can still be used in dropRawBuffer before dropping the reference.

Depends on D151008

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1778077 part 3 - Optimize non-Wasm SharedArrayBuffers. r?sfink!

The Wasm-specific fields are moved from SharedArrayRawBuffer into a new derived class,
WasmSharedArrayRawBuffer. This is similar to how non-shared buffers use WasmArrayRawBuffer.

The non-Wasm allocation code now uses calloc instead of mmap. This is also more like
how non-shared buffers work.

These changes make the non-Wasm SABs a lot more lightweight. This will help fix bug 1777231
and similar issues.

Depends on D151009

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1778077 part 4 - Call WasmSharedArrayRawBuffer's destructor to ensure the mutex is destroyed. r?sfink!

This fixes a pre-existing issue: Mutex has a destructor so we should call it.

Depends on D151010

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/32fcf7ae995e
part 1 - Inline SharedArrayRawBuffer::AllocateInternal into the two callers. r=sfink
https://hg.mozilla.org/integration/autoland/rev/3cc226c5c2a7
part 2 - Move dropReference call into dropRawBuffer. r=sfink
https://hg.mozilla.org/integration/autoland/rev/401aac8b1523
part 3 - Optimize non-Wasm SharedArrayBuffers. r=sfink
https://hg.mozilla.org/integration/autoland/rev/ac06b42c5b02
part 4 - Call WasmSharedArrayRawBuffer's destructor to ensure the mutex is destroyed. r=sfink

Comment 6

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/32fcf7ae995e
https://hg.mozilla.org/mozilla-central/rev/3cc226c5c2a7
https://hg.mozilla.org/mozilla-central/rev/401aac8b1523
https://hg.mozilla.org/mozilla-central/rev/ac06b42c5b02