Stream: git-wasmtime

Topic: wasmtime / PR #12123 [coop-threading] Track concurrent st...

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 10:15):

TartanLlama opened PR #12123 from TartanLlama:sy/sync-multithreading to bytecodealliance:main:

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view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 10:17):

TartanLlama edited PR #12123:

Threads are currently not created on sync->sync export calls, sync host->guest calls, and module-level start function calls. This PR adds support to this for all of these.

Fixes #11954

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 10:31):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 10:53):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:02):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:17):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:25):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:28):

TartanLlama edited PR #12123:

Threads are currently not created on sync->sync export calls, sync host->guest calls, and module-level start function calls. This PR adds support to this for all of these.

I added a component-model-async feature to wasmtime-environ so that sync->sync adapters are compiled as they were originally for wasip2 code, avoiding changing performance characteristics.

Fixes #11954

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:29):

TartanLlama edited PR #12123:

Threads are currently not created on sync->sync export calls, sync host->guest calls, and module-level start function calls. This PR adds support to this for all of these.

I added a component-model-async feature to wasmtime-environ so that sync->sync adapters are compiled as they were originally for wasip2 code, avoiding changing performance characteristics.

Rather than use the existing prepare_call + start_call machinery, I introduced sync_to_sync_enter/exit_call intrinsics to avoid adding additional host frames to the stack for sync calls

Fixes #11954

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 11:31):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 12:23):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 04 2025 at 12:28):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 08 2025 at 14:56):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 08 2025 at 15:09):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 10 2025 at 13:06):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 10 2025 at 13:09):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 10 2025 at 13:41):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 10 2025 at 13:54):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 13:13):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 13:30):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 13:31):

TartanLlama updated PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 13:33):

TartanLlama edited PR #12123:

Threads are currently not created on sync->sync export calls, sync host->guest calls, and module-level start function calls. This PR adds support to this for all of these.

I added a component-model-async feature to wasmtime-environ so that sync->sync adapters are compiled as they were originally for wasip2 code, avoiding changing performance characteristics.

Rather than use the existing prepare_call + start_call machinery, I introduced sync_to_sync_enter/exit_call intrinsics to avoid adding additional host frames to the stack for sync calls.

Currently, doing operations that require thread state inside post_return functions is unsupported. If we're happy merging this as-is and creating an issue to resolve this later, we can do so, or I can try and address it prior to merging.

Fixes #11954

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 15:05):

TartanLlama has marked PR #12123 as ready for review.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 15:05):

TartanLlama requested abrown for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 15:05):

TartanLlama requested wasmtime-compiler-reviewers for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 15:05):

TartanLlama requested pchickey for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Dec 11 2025 at 15:05):

TartanLlama requested wasmtime-core-reviewers for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Jan 07 2026 at 17:24):

dicej requested alexcrichton for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Jan 07 2026 at 17:24):

dicej requested dicej for a review on PR #12123.

view this post on Zulip Wasmtime GitHub notifications bot (Jan 07 2026 at 17:37):

dicej commented on PR #12123:

I've only skimmed this so far; it looks generally reasonable, but I expect it will conflict with https://github.com/bytecodealliance/wasmtime/pull/12153, which I'm about to split into smaller PRs per @alexcrichton's request.

Given that the component-model-async feature is now enabled by default, we'll need to be conscious of the overhead of e.g. calling sync_to_sync_enter_call and sync_to_sync_exit_call per this Zulip topic. In https://github.com/bytecodealliance/wasmtime/pull/12153, I had to get creative and sometimes lazily push GuestTasks and GuestThreads as necessary to avoid pessimizing sync-to-sync adapters. @TartanLlama we should chat sometime about if (and if so, how) we could do a similar optimization here.

Last updated: Jan 09 2026 at 13:15 UTC