Stream: git-wasmtime

Topic: wasmtime / PR #14605 Allow single byte GC page size

Wasmtime GitHub notifications bot (Oct 07 2026 at 14:46):

simolus3 opened PR #14605 from simolus3:gc-page-size to bytecodealliance:main:

This adds the gc_heap_page_size_log2 option, which can be used to control the page size of the memory used for GC allocations.

Matching an existing assertion on memory page sizes, the only allowed values are 0 (1 byte pages) and 16 (64k pages). Exposing this uncovered a few issues related to how memory growth is computed (which didn't take alignment into account and could thus grow memory by an incorrect amount, something that 64k pages hide).

Closes https://github.com/bytecodealliance/wasmtime/issues/14523.

Wasmtime GitHub notifications bot (Oct 07 2026 at 14:46):

simolus3 requested alexcrichton for a review on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 14:46):

simolus3 requested wasmtime-core-reviewers for a review on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 14:46):

simolus3 requested wasmtime-default-reviewers for a review on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 15:54):

github-actions[bot] added the label wasmtime:config on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 15:54):

github-actions[bot] added the label wasmtime:api on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 15:54):

github-actions[bot] added the label wasmtime:ref-types on PR #14605.

Wasmtime GitHub notifications bot (Oct 07 2026 at 16:51):

github-actions[bot] commented on PR #14605:

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Wasmtime GitHub notifications bot (Oct 07 2026 at 17:50):

github-actions[bot] commented on PR #14605:

Label Messager: wasmtime:config

It looks like you are changing Wasmtime's configuration options. Make sure to
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Wasmtime GitHub notifications bot (Oct 07 2026 at 22:30):

:memo: alexcrichton submitted PR review.

Wasmtime GitHub notifications bot (Oct 07 2026 at 22:30):

:speech_balloon: alexcrichton created PR review comment:

Given how long these tests take in CI, we'll want to avoid adding this. That being said it's good to confirm here (and probably you did this locally too) that this works.

To replace this though -- can you update the fuzzing crate to configure this option?

Wasmtime GitHub notifications bot (Oct 07 2026 at 22:30):

:speech_balloon: alexcrichton created PR review comment:

This is pertty different from the code it's replacing and it additionally has an unchecked multiplication which was previously saturating -- could you comment a bit more on this change?

Wasmtime GitHub notifications bot (Oct 07 2026 at 22:30):

:speech_balloon: alexcrichton created PR review comment:

This feels not quite accurate in that shouldn't the alignment be an argument? With v128 in the GC heap I'd expect that alignments could get up to 16. (or am I misremembering and everything is aligned at 8?)

Last updated: Oct 11 2026 at 04:10 UTC