wasmtime / PR #9484 Add the "null" garbage collector · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / PR #9484 Add the "null" garbage collector

Wasmtime GitHub notifications bot (Oct 17 2024 at 17:23):

fitzgen requested alexcrichton for a review on PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 17:23):

fitzgen requested wasmtime-core-reviewers for a review on PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 17:23):

fitzgen requested wasmtime-default-reviewers for a review on PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 17:23):

fitzgen opened PR #9484 from fitzgen:null-gc to bytecodealliance:main:

The null collector does not actually collect any garbage, it simply bump-allocates until the heap is exhausted, at which point further allocation attempts will fail. It does not require any GC barriers.

Users can configure which collector to use via the wasmtime::Config::collector method or the -C collector=drc|null CLI flag. The wasmtime::Collector enumeration, similar to the wasmtime::Strategy enumeration but for choosing a collector rather than a compiler, additionally has a table summarizing the properties and characteristics of our current set of collector implementations.

Finally, we also run .wast tests that exercise GC types under both the DRC and null collectors. I tried to avoid running tests that are not related to GC under both configurations just to avoid a combinatorial blow up.

(This PR builds on top of https://github.com/bytecodealliance/wasmtime/pull/9483, which is the first commit.)

Wasmtime GitHub notifications bot (Oct 17 2024 at 17:27):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 18:40):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 18:46):

fitzgen edited PR #9484:

The null collector does not actually collect any garbage, it simply bump-allocates until the heap is exhausted, at which point further allocation attempts will fail. It does not require any GC barriers.

Users can configure which collector to use via the wasmtime::Config::collector method or the -C collector=drc|null CLI flag. The wasmtime::Collector enumeration, similar to the wasmtime::Strategy enumeration but for choosing a collector rather than a compiler, additionally has a table summarizing the properties and characteristics of our current set of collector implementations.

Finally, we also run .wast tests that exercise GC types under both the DRC and null collectors. I tried to avoid running tests that are not related to GC under both configurations just to avoid a combinatorial blow up.

Wasmtime GitHub notifications bot (Oct 17 2024 at 18:49):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 18:58):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 19:52):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 17 2024 at 21:44):

github-actions[bot] commented on PR #9484:

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Wasmtime GitHub notifications bot (Oct 17 2024 at 22:45):

github-actions[bot] commented on PR #9484:

Label Messager: wasmtime:config

It looks like you are changing Wasmtime's configuration options. Make sure to
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Often, all that is required of you is to ensure that there is a knob for this
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[fuzzing-config]: https://github.com/bytecodealliance/wasmtime/blob/ca0e8d0a1d8cefc0496dba2f77a670571d8fdcab/crates/fuzzing/src/generators.rs#L182-L194
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Wasmtime GitHub notifications bot (Oct 18 2024 at 16:37):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 18 2024 at 16:37):

fitzgen requested wasmtime-fuzz-reviewers for a review on PR #9484.

Wasmtime GitHub notifications bot (Oct 18 2024 at 16:37):

fitzgen edited a comment on PR #9484:

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>

[x] 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 (Oct 18 2024 at 16:37):

fitzgen edited a comment on PR #9484:

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 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>

[x] 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 (Oct 18 2024 at 16:37):

fitzgen edited a comment on PR #9484:

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 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>

[x] 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>

[x] 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 (Oct 18 2024 at 17:44):

github-actions[bot] commented on PR #9484:

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Wasmtime GitHub notifications bot (Oct 21 2024 at 09:31):

alexcrichton submitted PR review:

Very nice! I like how this shaped up. I hope the #[cfg] wasn't too much to add, but it all looks relatively focused to be so it's hopefully just a one-time cost.

Wasmtime GitHub notifications bot (Oct 21 2024 at 09:31):

alexcrichton created PR review comment:

To confirm this technically isn't necessary right? (to specify -C collector=drc)

I think it's good to have in the test for future-proofing, but I want to double-check that as-is in isolation this isn't needed if we make no more changes to wasmtime in the future

Wasmtime GitHub notifications bot (Oct 21 2024 at 09:31):

alexcrichton created PR review comment:

Instead of self.features() can you use the features that are in scope from above?

Wasmtime GitHub notifications bot (Oct 21 2024 at 09:31):

alexcrichton created PR review comment:

Could this get pushed into a Result-return of Config::collector or within Config::validate?

Wasmtime GitHub notifications bot (Oct 21 2024 at 16:50):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Oct 21 2024 at 16:50):

fitzgen created PR review comment:

Correct, this is just future-proofing for if/when we change the default collector.

Wasmtime GitHub notifications bot (Oct 21 2024 at 18:31):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 21 2024 at 18:31):

fitzgen has enabled auto merge for PR #9484.

Wasmtime GitHub notifications bot (Oct 21 2024 at 18:35):

fitzgen commented on PR #9484:

Very nice! I like how this shaped up.

Thanks!

I hope the #[cfg] wasn't too much to add, but it all looks relatively focused to be so it's hopefully just a one-time cost.

Indeed, it was mostly some shuffling to get rid of the disabled collector impl and then realizing that various things that were DRC-specific modules could actually be made a little more generic and reused with other collectors. I think adding the copying collector will be relatively small in comparison to this PR, which is kind of funny.

Wasmtime GitHub notifications bot (Oct 21 2024 at 23:47):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 21 2024 at 23:47):

fitzgen has enabled auto merge for PR #9484.

Wasmtime GitHub notifications bot (Oct 30 2024 at 20:23):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 30 2024 at 20:57):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 30 2024 at 20:57):

fitzgen has enabled auto merge for PR #9484.

Wasmtime GitHub notifications bot (Oct 31 2024 at 17:33):

fitzgen updated PR #9484.

Wasmtime GitHub notifications bot (Oct 31 2024 at 17:34):

fitzgen has enabled auto merge for PR #9484.

Wasmtime GitHub notifications bot (Oct 31 2024 at 18:02):

fitzgen merged PR #9484.

Last updated: Nov 22 2024 at 17:03 UTC