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reduce number of task in async_module #5959

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merged 1 commit into from
Sep 15, 2023
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reduce number of task in async_module #5959

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27 changes: 10 additions & 17 deletions crates/turbopack-ecmascript/src/references/async_module.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use swc_core::{
ecma::ast::{ArrayLit, ArrayPat, Expr, Ident, Pat, Program},
quote,
};
use turbo_tasks::{primitives::Bools, trace::TraceRawVcs, TryFlatJoinIterExt, Value, Vc};
use turbo_tasks::{trace::TraceRawVcs, TryFlatJoinIterExt, Value, Vc};
use turbopack_core::chunk::availability_info::AvailabilityInfo;

use super::esm::base::ReferencedAsset;
Expand Down Expand Up @@ -102,17 +102,6 @@ struct AsyncModuleScc {
#[turbo_tasks::value(transparent)]
struct OptionAsyncModuleScc(Option<Vc<AsyncModuleScc>>);

#[turbo_tasks::function]
async fn is_placeable_self_async(
placeable: Vc<Box<dyn EcmascriptChunkPlaceable>>,
) -> Result<Vc<bool>> {
let Some(async_module) = &*placeable.get_async_module().await? else {
return Ok(Vc::cell(false));
};

Ok(async_module.is_self_async())
}

#[turbo_tasks::value_impl]
impl AsyncModuleScc {
#[turbo_tasks::function]
Expand All @@ -124,19 +113,23 @@ impl AsyncModuleScc {
async fn is_async(self: Vc<Self>) -> Result<Vc<bool>> {
let this = self.await?;

let mut bools = Vec::new();

for placeable in &*this.scc.await? {
bools.push(is_placeable_self_async(*placeable));
if let Some(async_module) = &*placeable.get_async_module().await? {
if *async_module.is_self_async().await? {
return Ok(Vc::cell(true));
}
}
}

for scc in &*this.scope.get_scc_children(this.scc).await? {
// Because we generated SCCs there can be no loops in the children, so calling
// recursively is fine.
bools.push(AsyncModuleScc::new(*scc, this.scope).is_async());
if *AsyncModuleScc::new(*scc, this.scope).is_async().await? {
return Ok(Vc::cell(true));
}
}

Ok(Vc::<Bools>::cell(bools).any())
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Is this faster because we've implemented early exiting, or because we no longer need to build up this Bools vc just to await it? Does this have implications for the just-approved https://github.com/vercel/next.js/blob/35fd8bcb0388420618a6ffb08ad5e93f716016c1/packages/next-swc/crates/next-api/src/project.rs#L706

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@sokra sokra Sep 15, 2023 •
edited
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early exist reduces the number of tasks. The Bools::any() also saves 1 task, but it's only a single one.

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Completions is technically similar, but no early exit is possible here. We could avoid 1 task by not using Completions::completed(), but it's only 1 task and it has effects on the invalidation: Without Completions::completed() it would need to rerun the current function when any completion fires. With Completions::completed() it only reruns Completions::completed() and doesn't need to rerun the current function.

There is a difference in how often these methods are called is_async is called many many times (for every module), while any_output_changed is only called once.

Ok(Vc::cell(false))
}
}

Expand Down