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stream: resolve perf regression introduced by V8 7.3 #28842

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stream: resolve perf regression introduced by V8 7.3 #28842

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a6e108a
stream: resolve perf regression introduced by V8 7.3
mcollina Jul 24, 2019
0b015f8
Update lib/_stream_writable.js
mcollina Jul 24, 2019
14bc169
Update lib/_stream_readable.js
mcollina Jul 25, 2019
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stream: resolve perf regression introduced by V8 7.3 
This commit contains two fixes:
1. use instanceof instead of Object.getPrototypeOf, as checking an
   object prototype with Object.getPrototypeOf is slower
   than an instanceof check.
2. avoid parseInt(undefined, 10) to get NaN as it regressed.

Fixes: #28586
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@mcollina
mcollina committed Jul 24, 2019
commit a6e108a97bd400e9320046241e121b2d024106b3
11 changes: 9 additions & 2 deletions lib/_stream_readable.js
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Expand Up @@ -256,7 +256,8 @@ function readableAddChunk(stream, chunk, encoding, addToFront) {
} else if (state.objectMode || chunk && chunk.length > 0) {
if (typeof chunk !== 'string' &&
!state.objectMode &&
Object.getPrototypeOf(chunk) !== Buffer.prototype) {
// Do not use Object.getPrototypeOf as it is slower.
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!(chunk instanceof Buffer)) {
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chunk = Stream._uint8ArrayToBuffer(chunk);
}

Expand Down Expand Up @@ -399,7 +400,13 @@ function howMuchToRead(n, state) {
// You can override either this method, or the async _read(n) below.
Readable.prototype.read = function(n) {
debug('read', n);
n = parseInt(n, 10);
// Same as parseInt(undefined, 10), however V8 7.3 performance regressed
// in this scenario, so we are doing it manually.
if (n === undefined) {
n = NaN;
} else if (!Number.isInteger(n)) {
n = parseInt(n, 10);
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}
const state = this._readableState;
const nOrig = n;

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3 changes: 2 additions & 1 deletion lib/_stream_writable.js
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Expand Up @@ -277,7 +277,8 @@ Writable.prototype.write = function(chunk, encoding, cb) {
var ret = false;
const isBuf = !state.objectMode && Stream._isUint8Array(chunk);

if (isBuf && Object.getPrototypeOf(chunk) !== Buffer.prototype) {
// Do not use Object.getPrototypeOf as it is slower.
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if (isBuf && !(chunk instanceof Buffer)) {
chunk = Stream._uint8ArrayToBuffer(chunk);
}

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