stream: cut promise churn in webstreams hot paths#65138

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Merged
aduh95 merged 3 commits into from
Aug 15, 2026
+145 −52
Merged

stream: cut promise churn in webstreams hot paths #65138

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3e4d2e4
benchmark: apply `highWaterMark` in webstreams `pipe-to`
mcollina Aug 8, 2026
ec1a8df
stream: cut promise churn in webstreams hot paths
mcollina Aug 8, 2026
2929417
stream: consolidate non-op algorithm callbacks
mcollina Aug 8, 2026
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10 changes: 4 additions & 6 deletions benchmark/webstreams/pipe-to.js
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Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
n: [5e5],
highWaterMarkR: [512, 1024, 2048, 4096],
highWaterMarkW: [512, 1024, 2048, 4096],
highWaterMarkR: [1, 1024, 4096],
highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
const b = Buffer.alloc(1024);
let i = 0;
const rs = new ReadableStream({
highWaterMark: highWaterMarkR,
pull: function(controller) {
if (i++ < n) {
controller.enqueue(b);
} else {
controller.close();
}
},
});
}, { highWaterMark: highWaterMarkR });
const ws = new WritableStream({
highWaterMark: highWaterMarkW,
write(chunk, controller) {},
close() { bench.end(n); },
});
}, { highWaterMark: highWaterMarkW });

bench.start();
rs.pipeTo(ws);
Expand Down
100 changes: 72 additions & 28 deletions lib/internal/webstreams/readablestream.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
cloneAsUint8Array,
copyArrayBuffer,
createPromiseCallback1Param,
createRawCallback1Param,
customInspect,
defaultSizeAlgorithm,
dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
getNonWritablePropertyDescriptor,
isBrandCheck,
kEmptyQueue,
kResolvedPromise,
kState,
kType,
lazyTransfer,
materializeQueue,
nonOpCallback,
nonOpCancel,
nonOpPull,
nonOpStart,
rejectedHandledRecord,
resetQueue,
resolvedRecord,
setPromiseHandled,
thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
writableStreamDefaultWriterRelease,
writableStreamDefaultWriterWriteWithRequest,
writerClosedPromise,
writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
}
const startAlgorithm = nonOpStart;
const startAlgorithm = nonOpCallback;

async function pullAlgorithm() {
const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
// the chunk travels through `pendingChunk`.
let pendingChunk;
let readRequest;
let readyHook;

// Ready promise rejection is handled by the destination-errored
// watcher.
function ignoreReadyRejection() {}

// Parks the pump on the destination's backpressure by installing a
// record that duck-types the writer's lazily-materialized
// [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
// when backpressure clears (after publishing the new backpressure
// state), which re-enters the pump directly instead of rotating a
// fresh promise record plus reaction per flip. The pipe holds the only
// reference to the writer, so the record is never observable as a real
// ready promise; the erroring/release paths probe `promise` via
// isPromisePending() and call `reject`, so it carries a real
// forever-pending promise and a no-op reject.
function parkOnReady() {
readyHook ??= {
promise: new Promise(nonOpCallback),
resolve: pump,
reject: ignoreReadyRejection,
};
writer[kState].ready = readyHook;
}

function forwardChunk() {
const chunk = pendingChunk;
pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
if (shuttingDown) return;

if (dest[kState].backpressure) {
PromisePrototypeThen(
writerReadyPromise(writer).promise,
pump,
ignoreReadyRejection);
parkOnReady();
return;
}

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
return;
}

// Yield to microtask queue between batches to allow events/signals
// to fire
queueMicrotask(pump);
// Park on backpressure directly: the ready hook resumes the pump
// when a completed write clears it.
if (dest[kState].backpressure) {
parkOnReady();
return;
}

// Yield to the microtask queue between batches so completed-write
// reactions and events/signals fire; a shared resolved promise
// enqueues the continuation at the same position as queueMicrotask
// without the per-batch scheduling overhead.
PromisePrototypeThen(kResolvedPromise, pump);
return;
}

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
// synchronous write during enqueue(). See WHATWG Streams spec
// "ReadableStreamPipeTo" step 15's "chunk steps".
pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
},
[kClose]() {},
[kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
// The microtask is required by the spec (ReadableStreamTee's
// "chunk steps" queue one).
pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
},
[kClose]() {
// The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
}

branch1 =
createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
branch2 =
createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

PromisePrototypeThen(
readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
defaultReadRequest ??= {
[kChunk](chunk) {
pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
},
[kClose]() {
reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
}

branch1 =
createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
branch2 =
createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
controller[kState].pullRejected =
(error) => readableStreamDefaultControllerError(controller, error);
}
PromisePrototypeThen(
controller[kState].pullAlgorithm(controller),
// The pull algorithm may be a raw callback (a wrapped user source.pull
// returns its result uncoerced; a synchronous throw surfaces here) or an
// internal algorithm that always returns a promise; thenAlgorithmResult
// handles both.
let result;
try {
result = controller[kState].pullAlgorithm(controller);
} catch (error) {
result = PromiseReject(error);
}
thenAlgorithmResult(
result,
controller[kState].pullFulfilled,
controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
const cancel = source?.cancel;
const startAlgorithm = start ?
FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
const cancelAlgorithm = cancel ?
createPromiseCallback1Param('source.cancel', cancel, source) :
nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
controller[kState].pullRejected =
(error) => readableByteStreamControllerError(controller, error);
}
PromisePrototypeThen(
controller[kState].pullAlgorithm(controller),
// See readableStreamDefaultControllerPull for the raw-callback contract.
let result;
try {
result = controller[kState].pullAlgorithm(controller);
} catch (error) {
result = PromiseReject(error);
}
thenAlgorithmResult(
result,
controller[kState].pullFulfilled,
controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
const autoAllocateChunkSize = source?.autoAllocateChunkSize;
const startAlgorithm = start ?
FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
const cancelAlgorithm = cancel ?
createPromiseCallback1Param('source.cancel', cancel, source) :
nonOpCancel;
Expand Down
53 changes: 45 additions & 8 deletions lib/internal/webstreams/util.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
validateFunction(fn, name);
return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
validateFunction(fn, name);
return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
if (result === null ||
(typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.
PromisePrototypeThen(kResolvedPromise, onFulfilled);
} else {
PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
}
}

function createPromiseCallback1Param(name, fn, thisArg) {
validateFunction(fn, name);
return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
createPromiseCallbackNoParams,
createPromiseCallback1Param,
createPromiseCallback2Params,
createRawCallback1Param,
createRawCallback2Params,
customInspect,
defaultSizeAlgorithm,
dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
isBrandCheck,
isPromisePending,
kEmptyQueue,
kResolvedPromise,
kState,
kType,
lazyTransfer,
materializeQueue,
nonOpCallback,
nonOpCancel,
nonOpFlush,
nonOpPull,
nonOpStart,
nonOpWrite,

peekQueueValue,
rejectedHandledRecord,
resetQueue,
resolvedRecord,
setPromiseHandled,
thenAlgorithmResult,
};
Loading
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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stream: cut promise churn in webstreams hot paths#65138

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Merged

aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
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Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
stream: cut promise churn in webstreams hot paths#65138

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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 Merged

aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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merged 3 commits into

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Aug 15, 2026

+145

−52

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stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
stream: cut promise churn in webstreams hot paths#65138

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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 Merged

aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
jasnell marked this conversation as resolved.

 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
stream: cut promise churn in webstreams hot paths#65138

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 Merged

aduh95
merged 3 commits into

from

Aug 15, 2026

+145

−52

 Merged


stream: cut promise churn in webstreams hot paths
#65138
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3e4d2e4

benchmark: apply `highWaterMark` in webstreams `pipe-to`


mcollina Aug 8, 2026
ec1a8df

stream: cut promise churn in webstreams hot paths


mcollina Aug 8, 2026
2929417

stream: consolidate non-op algorithm callbacks


mcollina Aug 8, 2026

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10 changes: 4 additions & 6 deletions
benchmark/webstreams/pipe-to.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -7,29 +7,27 @@ const {

const bench = common.createBenchmark(main, {
 n: [5e5],
 highWaterMarkR: [512, 1024, 2048, 4096],
 highWaterMarkW: [512, 1024, 2048, 4096],
 highWaterMarkR: [1, 1024, 4096],
 highWaterMarkW: [1, 1024, 4096],
});


async function main({ n, highWaterMarkR, highWaterMarkW }) {
 const b = Buffer.alloc(1024);
 let i = 0;
 const rs = new ReadableStream({
 highWaterMark: highWaterMarkR,
 pull: function(controller) {
 if (i++ < n) {
 controller.enqueue(b);
 } else {
 controller.close();
 }
 },
 });
 }, { highWaterMark: highWaterMarkR });
 const ws = new WritableStream({
 highWaterMark: highWaterMarkW,
 write(chunk, controller) {},
 close() { bench.end(n); },
 });
 }, { highWaterMark: highWaterMarkW });

 bench.start();
 rs.pipeTo(ws);
Expand Down

100 changes: 72 additions & 28 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -101,6 +101,7 @@ const {
 cloneAsUint8Array,
 copyArrayBuffer,
 createPromiseCallback1Param,
 createRawCallback1Param,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -110,17 +111,18 @@ const {
 getNonWritablePropertyDescriptor,
 isBrandCheck,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpPull,
 nonOpStart,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
} = require('internal/webstreams/util');

const {
Expand All@@ -137,7 +139,6 @@ const {
 writableStreamDefaultWriterRelease,
 writableStreamDefaultWriterWriteWithRequest,
 writerClosedPromise,
 writerReadyPromise,
} = require('internal/webstreams/writablestream');

const { Buffer } = require('buffer');
Expand DownExpand Up@@ -1445,7 +1446,7 @@ function readableStreamFromIterable(iterable) {
 if (iterator === null || (typeof iterator !== 'object' && typeof iterator !== 'function')) {
 throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
 }
 const startAlgorithm = nonOpStart;
 const startAlgorithm = nonOpCallback;

 async function pullAlgorithm() {
 const iterResult = await iterator.next();
Expand DownExpand Up@@ -1664,11 +1665,31 @@ function readableStreamPipeTo(
 // the chunk travels through `pendingChunk`.
 let pendingChunk;
 let readRequest;
 let readyHook;

 // Ready promise rejection is handled by the destination-errored
 // watcher.
 function ignoreReadyRejection() {}

 // Parks the pump on the destination's backpressure by installing a
 // record that duck-types the writer's lazily-materialized
 // [[readyPromise]] record: writableStreamUpdateBackpressure resolves it
 // when backpressure clears (after publishing the new backpressure
 // state), which re-enters the pump directly instead of rotating a
 // fresh promise record plus reaction per flip. The pipe holds the only
 // reference to the writer, so the record is never observable as a real
 // ready promise; the erroring/release paths probe `promise` via
 // isPromisePending() and call `reject`, so it carries a real
 // forever-pending promise and a no-op reject.
 function parkOnReady() {
 readyHook ??= {
 promise: new Promise(nonOpCallback),
 resolve: pump,
 reject: ignoreReadyRejection,
 };
 writer[kState].ready = readyHook;
 }

 function forwardChunk() {
 const chunk = pendingChunk;
 pendingChunk = undefined;
Expand All@@ -1680,10 +1701,7 @@ function readableStreamPipeTo(
 if (shuttingDown) return;

 if (dest[kState].backpressure) {
 PromisePrototypeThen(
 writerReadyPromise(writer).promise,
 pump,
 ignoreReadyRejection);
 parkOnReady();
 return;
 }

Expand DownExpand Up@@ -1728,9 +1746,18 @@ function readableStreamPipeTo(
 return;
 }

 // Yield to microtask queue between batches to allow events/signals
 // to fire
 queueMicrotask(pump);
 // Park on backpressure directly: the ready hook resumes the pump
 // when a completed write clears it.
 if (dest[kState].backpressure) {
 parkOnReady();
 return;
 }

 // Yield to the microtask queue between batches so completed-write
 // reactions and events/signals fire; a shared resolved promise
 // enqueues the continuation at the same position as queueMicrotask
 // without the per-batch scheduling overhead.
 PromisePrototypeThen(kResolvedPromise, pump);
 return;
 }

Expand All@@ -1742,7 +1769,7 @@ function readableStreamPipeTo(
 // synchronous write during enqueue(). See WHATWG Streams spec
 // "ReadableStreamPipeTo" step 15's "chunk steps".
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {},
 [kError]() {},
Expand DownExpand Up@@ -1857,7 +1884,7 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 // The microtask is required by the spec (ReadableStreamTee's
 // "chunk steps" queue one).
 pendingChunk = value;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 // The `process.nextTick()` is not part of the spec.
Expand DownExpand Up@@ -1901,9 +1928,9 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
 }

 branch1 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel1Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel1Algorithm);
 branch2 =
 createReadableStream(nonOpStart, pullAlgorithm, cancel2Algorithm);
 createReadableStream(nonOpCallback, pullAlgorithm, cancel2Algorithm);

 PromisePrototypeThen(
 readerClosedPromise(reader).promise,
Expand DownExpand Up@@ -2010,7 +2037,7 @@ function readableByteStreamTee(stream) {
 defaultReadRequest ??= {
 [kChunk](chunk) {
 pendingChunk = chunk;
queueMicrotask(forwardChunk);
PromisePrototypeThen(kResolvedPromise, forwardChunk);
 },
 [kClose]() {
 reading = false;
Expand DownExpand Up@@ -2189,9 +2216,9 @@ function readableByteStreamTee(stream) {
 }

 branch1 =
 createReadableByteStream(nonOpStart, pull1Algorithm, cancel1Algorithm);
 createReadableByteStream(nonOpCallback, pull1Algorithm, cancel1Algorithm);
 branch2 =
 createReadableByteStream(nonOpStart, pull2Algorithm, cancel2Algorithm);
 createReadableByteStream(nonOpCallback, pull2Algorithm, cancel2Algorithm);

 forwardReaderError(reader);

Expand DownExpand Up@@ -2699,8 +2726,18 @@ function readableStreamDefaultControllerPull(controller) {
 controller[kState].pullRejected =
 (error) => readableStreamDefaultControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // The pull algorithm may be a raw callback (a wrapped user source.pull
 // returns its result uncoerced; a synchronous throw surfaces here) or an
 // internal algorithm that always returns a promise; thenAlgorithmResult
 // handles both.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -2824,10 +2861,10 @@ function setupReadableStreamDefaultControllerFromSource(
 const cancel = source?.cancel;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand DownExpand Up@@ -3519,8 +3556,15 @@ function readableByteStreamControllerCallPullIfNeeded(controller) {
 controller[kState].pullRejected =
 (error) => readableByteStreamControllerError(controller, error);
 }
 PromisePrototypeThen(
 controller[kState].pullAlgorithm(controller),
 // See readableStreamDefaultControllerPull for the raw-callback contract.
 let result;
 try {
 result = controller[kState].pullAlgorithm(controller);
 } catch (error) {
 result = PromiseReject(error);
 }
 thenAlgorithmResult(
 result,
 controller[kState].pullFulfilled,
 controller[kState].pullRejected);
}
Expand DownExpand Up@@ -3698,10 +3742,10 @@ function setupReadableByteStreamControllerFromSource(
 const autoAllocateChunkSize = source?.autoAllocateChunkSize;
 const startAlgorithm = start ?
 FunctionPrototypeBind(start, source, controller) :
nonOpStart;
nonOpCallback;
 const pullAlgorithm = pull ?
createPromiseCallback1Param('source.pull', pull, source) :
nonOpPull;
createRawCallback1Param('source.pull', pull, source) :
nonOpCallback;
 const cancelAlgorithm = cancel ?
 createPromiseCallback1Param('source.cancel', cancel, source) :
 nonOpCancel;
Expand Down

53 changes: 45 additions & 8 deletions
lib/internal/webstreams/util.js

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Original file line numberDiff line numberDiff line change
Expand Up@@ -338,6 +338,40 @@ function createPromiseCallbackNoParams(name, fn, thisArg) {
 return async () => FunctionPrototypeCall(fn, thisArg);
}

// Raw variants that skip the async wrapper's implicit result promise.
// Consumers of a raw callback invoke it inside try/catch and route the
// result through thenAlgorithmResult() below.
function createRawCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg) => FunctionPrototypeCall(fn, thisArg, arg);
}

function createRawCallback2Params(name, fn, thisArg) {
 validateFunction(fn, name);
 return (arg1, arg2) => FunctionPrototypeCall(fn, thisArg, arg1, arg2);
}

// A single shared, forever-resolved promise used to enqueue a reaction at
// the next microtask checkpoint without allocating a fresh promise.
const kResolvedPromise = PromiseResolve();

// Wires the (possibly non-thenable) result of an underlying algorithm
// callback to its fulfilled/rejected continuations. A non-thenable result
// means fulfillment is guaranteed and no then() lookup is observable, so
// the fulfillment step is enqueued directly at the exact microtask
// position the coerced promise's reaction would have had, skipping the
// per-chunk promise allocation. For thenable results PromiseResolve()
// matches the spec's "a promise resolved with" conversion (identity for
// native promises).
function thenAlgorithmResult(result, onFulfilled, onRejected) {
 if (result === null ||
 (typeof result !== 'object' && typeof result !== 'function')) {
Comment thread
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 PromisePrototypeThen(kResolvedPromise, onFulfilled);
 } else {
 PromisePrototypeThen(PromiseResolve(result), onFulfilled, onRejected);
 }
}

function createPromiseCallback1Param(name, fn, thisArg) {
 validateFunction(fn, name);
 return async (arg) => FunctionPrototypeCall(fn, thisArg, arg);
Expand DownExpand Up@@ -384,14 +418,14 @@ function setPromiseHandled(promise) {

async function nonOpFlush() {}

function nonOpStart() {}

async function nonOpPull() {}
// Shared non-op for the start/pull/write algorithm callbacks, which all
// follow the raw-callback contract (see createRawCallback*): the
// non-thenable return takes the allocation-free fast path in
// thenAlgorithmResult().
function nonOpCallback() {}

async function nonOpCancel() {}

async function nonOpWrite() {}

let transfer;
function lazyTransfer() {
 if (transfer === undefined)
Expand All@@ -411,6 +445,8 @@ module.exports = {
 createPromiseCallbackNoParams,
 createPromiseCallback1Param,
 createPromiseCallback2Params,
 createRawCallback1Param,
 createRawCallback2Params,
 customInspect,
 defaultSizeAlgorithm,
 dequeueValue,
Expand All@@ -421,18 +457,19 @@ module.exports = {
 isBrandCheck,
 isPromisePending,
 kEmptyQueue,
 kResolvedPromise,
 kState,
 kType,
 lazyTransfer,
 materializeQueue,
 nonOpCallback,
 nonOpCancel,
 nonOpFlush,
 nonOpPull,
 nonOpStart,
 nonOpWrite,

 peekQueueValue,
 rejectedHandledRecord,
 resetQueue,
 resolvedRecord,
 setPromiseHandled,
 thenAlgorithmResult,
};
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