Stream: git-wasmtime

Topic: wasmtime / PR #13932 Add configurable costs for variable-...

Wasmtime GitHub notifications bot (Jul 22 2026 at 11:40):

d-sonuga opened PR #13932 from d-sonuga:var-cost-op to bytecodealliance:main:

Closes https://github.com/bytecodealliance/wasmtime/issues/13931.

Previously, variable cost operators like memory.fill were charged a constant non-configurable amount of fuel per byte. This extends OperatorCost with a VariableOperatorCost table so embedders can configure costs for operators whose work depends on runtime operands.

Wasmtime GitHub notifications bot (Jul 22 2026 at 11:40):

d-sonuga requested cfallin for a review on PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 11:40):

d-sonuga requested wasmtime-compiler-reviewers for a review on PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 11:40):

d-sonuga requested wasmtime-core-reviewers for a review on PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 12:15):

d-sonuga updated PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 14:25):

github-actions[bot] added the label wasmtime:api on PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 14:25):

github-actions[bot] added the label wasmtime:config on PR #13932.

Wasmtime GitHub notifications bot (Jul 22 2026 at 15:20):

github-actions[bot] commented on PR #13932:

Label Messager: wasmtime:config

It looks like you are changing Wasmtime's configuration options. Make sure to
complete this check list:

• [ ] If you added a new Config method, you wrote extensive documentation for
  it.

  <details>

  Our documentation should be of the following form:

  ```text
  Short, simple summary sentence.

  More details. These details can be multiple paragraphs. There should be
  information about not just the method, but its parameters and results as
  well.

  Is this method fallible? If so, when can it return an error?

  Can this method panic? If so, when does it panic?

  Example

  Optional example here.
  ```

  </details>

• [ ] If you added a new Config method, or modified an existing one, you
  ensured that this configuration is exercised by the fuzz targets.

  <details>

  For example, if you expose a new strategy for allocating the next instance
  slot inside the pooling allocator, you should ensure that at least one of our
  fuzz targets exercises that new strategy.

  Often, all that is required of you is to ensure that there is a knob for this
  configuration option in [wasmtime_fuzzing::Config][fuzzing-config] (or one
  of its nested structs).

  Rarely, this may require authoring a new fuzz target to specifically test this
  configuration. See [our docs on fuzzing][fuzzing-docs] for more details.

  </details>

• [ ] If you are enabling a configuration option by default, make sure that it
  has been fuzzed for at least two weeks before turning it on by default.

[fuzzing-config]: https://github.com/bytecodealliance/wasmtime/blob/ca0e8d0a1d8cefc0496dba2f77a670571d8fdcab/crates/fuzzing/src/generators.rs#L182-L194
[fuzzing-docs]: https://docs.wasmtime.dev/contributing-fuzzing.html

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Wasmtime GitHub notifications bot (Jul 27 2026 at 19:20):

:thumbs_up: cfallin submitted PR review:

This looks reasonable overall to me (and sorry for the delay in reviewing) -- just a few comments below. Thanks!

Wasmtime GitHub notifications bot (Jul 27 2026 at 19:20):

:speech_balloon: cfallin created PR review comment:

Is this drop necessary? It seems like lifetime inference should do the right thing here...

Wasmtime GitHub notifications bot (Jul 27 2026 at 19:20):

:speech_balloon: cfallin created PR review comment:

It looks like this single call to translate_entity_fill is more or less what translate_table_fill does -- any reason to remove the abstraction layer here?

Wasmtime GitHub notifications bot (Jul 28 2026 at 10:35):

d-sonuga updated PR #13932.

Wasmtime GitHub notifications bot (Jul 28 2026 at 10:38):

:memo: d-sonuga submitted PR review.

Wasmtime GitHub notifications bot (Jul 28 2026 at 10:38):

:speech_balloon: d-sonuga created PR review comment:

Right, it's not. I've removed it.

Wasmtime GitHub notifications bot (Jul 28 2026 at 10:43):

:memo: d-sonuga submitted PR review.

Wasmtime GitHub notifications bot (Jul 28 2026 at 10:43):

:speech_balloon: d-sonuga created PR review comment:

translate_entity_fill now takes a cost per element. translate_table_fill now always calls it with the configured cost for table.fill per element. But table.grow has its own separate cost per element so it calls translate_entity_fill directly.

Wasmtime GitHub notifications bot (Jul 28 2026 at 15:01):

:memo: cfallin submitted PR review.

Wasmtime GitHub notifications bot (Jul 28 2026 at 15:01):

:speech_balloon: cfallin created PR review comment:

Ah, right, missed that -- thanks!

Wasmtime GitHub notifications bot (Jul 28 2026 at 15:01):

cfallin added PR #13932 Add configurable costs for variable-work operators (#13931) to the merge queue

Wasmtime GitHub notifications bot (Jul 28 2026 at 15:27):

github-merge-queue[bot] removed PR #13932 Add configurable costs for variable-work operators (#13931) from the merge queue

Last updated: Jul 29 2026 at 05:03 UTC