wasmtime / PR #14045 Remove preemption points in bulk ope... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / PR #14045 Remove preemption points in bulk ope...

Wasmtime GitHub notifications bot (Jul 31 2026 at 15:16):

alexcrichton opened PR #14045 from alexcrichton:less-preemption to bytecodealliance:main:

This commit updates the translation of bulk operations such as memory.grow which were recently refactored to not have preemption points within the operation itself. Preemption points within the operation, while useful for very large operations, expose internal and intermediate state to embedders and the rest of the runtime. For example tables that are grown are initially filled with null, which may not be valid for the table's type. These bulk operations didn't recompute pointers/indices after a possible preemption meaning if memories were grown/moved then it would cause faults. In general this is seen as too risky of an operation to perform.

The fix in this commit is to move all preemption checks to the start of the operation itself. This means that bulk operations continue to be metered with a cost proportional to the size of the operation for fuel, and they all contain an initial epoch check for epochs. Once the operation is committed to, however, there's no cancelling it and it'll continue to run. In practice this means that extremely large copies, for example, can blow the epoch budget. To re-add preemption checks within the operation, however, will require very careful reintroduction to avoid these sorts of problems/faults.

Wasmtime GitHub notifications bot (Jul 31 2026 at 15:16):

alexcrichton requested cfallin for a review on PR #14045.

Wasmtime GitHub notifications bot (Jul 31 2026 at 15:16):

alexcrichton requested wasmtime-compiler-reviewers for a review on PR #14045.

Wasmtime GitHub notifications bot (Jul 31 2026 at 15:16):

alexcrichton requested wasmtime-core-reviewers for a review on PR #14045.

Wasmtime GitHub notifications bot (Jul 31 2026 at 16:17):

github-actions[bot] added the label wasmtime:api on PR #14045.

Wasmtime GitHub notifications bot (Jul 31 2026 at 16:17):

github-actions[bot] added the label wasmtime:config on PR #14045.

Wasmtime GitHub notifications bot (Jul 31 2026 at 17:11):

github-actions[bot] commented on PR #14045:

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