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perf: warmup next queued worker #8755

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perf: warmup next queued worker #8755

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14 changes: 12 additions & 2 deletions packages/vitest/src/node/pools/pool.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ interface QueuedTask {
task: PoolTask
resolver: ReturnType<typeof withResolvers>
method: 'run' | 'collect'
warmRunner?: Promise<PoolRunner>
}

interface ActiveTask extends QueuedTask {
Expand Down Expand Up @@ -67,11 +68,11 @@ export class Pool {
return
}

const { task, resolver, method } = this.queue.shift()!
const { task, resolver, method, warmRunner } = this.queue.shift()!

try {
let isMemoryLimitReached = false
const runner = this.getPoolRunner(task, method)
const runner = warmRunner ? await warmRunner : this.getPoolRunner(task, method)
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@AriPerkkio AriPerkkio Oct 22, 2025

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In the orignal PR I had this line as

const runner = (await warmRunner) || this.getPoolRunner(task, method)

... which broke everything and we had to drop this change. I though these two would be equivalent but no 🤔


const activeTask = { task, resolver, method, cancelTask }
this.activeTasks.push(activeTask)
Expand Down Expand Up @@ -123,6 +124,14 @@ export class Pool {
poolId,
})

const next = this.queue.find(entry => !entry.warmRunner && entry.task.isolate)

// Warmup the next runtime. This will start the dynamic imports inside the worker early.
if (next) {
const warmRunner = this.getPoolRunner(next.task, next.method)
next.warmRunner = warmRunner.start().then(() => warmRunner)
}

await resolver.promise

const index = this.activeTasks.indexOf(activeTask)
Expand Down Expand Up @@ -175,6 +184,7 @@ export class Pool {
if (pendingTasks.length) {
const error = new Error('Cancelled')
pendingTasks.forEach(task => task.resolver.reject(error))
await Promise.all(pendingTasks.map(task => task.warmRunner?.then(runner => runner.stop())))
}

const activeTasks = this.activeTasks.splice(0)
Expand Down
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