1861078 - Optimize stack map finding during tracing

Status: RESOLVED FIXED

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

Description

[Ryan Hunt [:rhunt]]

wasm::StackMaps is a sorted list and we do a binary search to find a stack map for each call frame when tracing roots. This can be expensive for large modules. We should consider using a hash map for this. I did see this showing up in barista3 profiles back in Feb of this year.

Comment 1

[Julien Pages [:jpages]]

Attachment: Bug 1861078 - wasm: make metadata offsets relative to CodeBlock->codeBase. r=rhunt

Metadata used offsets to the beginning of code segment. Change that to use
offsets relative to the beginning of CodeBlock. This allows us to avoid offseting
metadata later on and prepare the work for simplification of stackmaps.

Comment 2

[Julien Pages [:jpages]]

Attachment: Bug 1861078 - wasm: Refactor stackmaps to use a hashmap instead of a vector.

Wasm stackmaps were stored in a sorted vector and traced at runtime with multiple
binary searches. Using hashmaps should reduce the complexity of iterating over stackmaps.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9a162cc369e3
wasm: make metadata offsets relative to CodeBlock->codeBase. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/e6dbc240ccbb
wasm: Refactor stackmaps to use a hashmap instead of a vector. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/2bb2770e86d0
apply code formatting via Lando

Comment 4

[Atila Butkovits]

Backed out for causing bustages complaining about ComputeCodeOffset.

Backout link: https://hg.mozilla.org/integration/autoland/rev/6db7ad98b50985f4cc72770d0104b01263e6a735

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=2bb2770e86d0e847e5c6328d52da3deedcb4780f&selectedTaskRun=Va-iHgUUTbWzrqJslHHMPQ.0

Failure log:
https://treeherder.mozilla.org/logviewer?job_id=496096679&repo=autoland&lineNumber=17180
https://treeherder.mozilla.org/logviewer?job_id=496096726&repo=autoland&lineNumber=40716

Comment 5

[Julien Pages [:jpages]]

I'll land the patch again after the code freeze, ending on March 3.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1a3bc285395f
wasm: make metadata offsets relative to CodeBlock->codeBase. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/bd2b8b0c2f35
wasm: Refactor stackmaps to use a hashmap instead of a vector. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/24eb5e44d488
apply code formatting via Lando

Comment 7

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/1a3bc285395f
https://hg.mozilla.org/mozilla-central/rev/bd2b8b0c2f35
https://hg.mozilla.org/mozilla-central/rev/24eb5e44d488