Wasmtime GitHub notifications bot (Mar 13 2026 at 00:04): Wasmtime GitHub notifications bot (Mar 13 2026 at 00:04):posborne opened PR #12772 from posborne:include-core-instance-size-in-compennt-instance-limits to bytecodealliance:main:
There exist several knobs for limiting the memory that might be consumed for metadata for components. For core module instances within a component, the two that previously existed to control metadata allocations have been:
- A: max_core_instances_per_component
- B: component_instance_size
These allow for an embedder to set an upper bound on memory used by a component's instances to A * B. This value could be quite large for some systems and it would be nice to be able to set a cap on the total memory that might be used for metadata across all instances while still allowing for a greater number of instances with the potential for a subset of those instances to be relatively large.
To allow for aggregate control over memory used within the runtime for componenets, the existing
max_component_instance_sizelimit is extended to consider both theVMComponentCtxsize as well as the aggregate size of all core instances in the component.The original changeset which introduced a separate config knob was #12768 which this replaces.
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Wasmtime GitHub notifications bot (Mar 13 2026 at 00:04):posborne requested wasmtime-core-reviewers for a review on PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 00:04):posborne requested alexcrichton for a review on PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 04:21):github-actions[bot] added the label wasmtime:api on PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 04:21):github-actions[bot] added the label wasmtime:config on PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 04:23):github-actions[bot] commented on PR #12772:
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Wasmtime GitHub notifications bot (Mar 13 2026 at 14:22):alexcrichton submitted PR review:
Thanks!
Wasmtime GitHub notifications bot (Mar 13 2026 at 15:52):posborne edited a comment on PR #12772:
Label Messager: wasmtime:config
It looks like you are changing Wasmtime's configuration options. Make sure to
complete this check list:
[x] If you added a new
Configmethod, 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
Configmethod, 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 nestedstructs).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 (Mar 13 2026 at 16:04):posborne updated PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 18:02):alexcrichton added PR #12772 Include core instance sizes in component_instance_size limit to the merge queue.
Wasmtime GitHub notifications bot (Mar 13 2026 at 18:26):github-merge-queue[bot] removed PR #12772 Include core instance sizes in component_instance_size limit from the merge queue.
Wasmtime GitHub notifications bot (Mar 13 2026 at 20:06):posborne updated PR #12772.
Wasmtime GitHub notifications bot (Mar 13 2026 at 20:21):alexcrichton added PR #12772 Include core instance sizes in component_instance_size limit to the merge queue.
Wasmtime GitHub notifications bot (Mar 13 2026 at 20:45):alexcrichton removed PR #12772 Include core instance sizes in component_instance_size limit from the merge queue.
Wasmtime GitHub notifications bot (Mar 13 2026 at 20:45):alexcrichton merged PR #12772.
Last updated: Mar 23 2026 at 16:19 UTC