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buffer: optimize writing short strings #54310

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buffer: optimize writing short strings #54310

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20 changes: 20 additions & 0 deletions benchmark/buffers/buffer-write-string-short.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
'use strict';

const common = require('../common.js');
const bench = common.createBenchmark(main, {
len: [0, 1, 8, 16, 32],
fallback: [1, 0],
n: [1e6],
});

function main({ len, n, fallback }) {
const buf = Buffer.allocUnsafe(len);
const string = fallback && len > 0
? Buffer.from('a'.repeat(len - 1) + '€').toString()

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'?' should be placed at the end of the line
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Can you fix the formatting issues?

: Buffer.from('a'.repeat(len)).toString()

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':' should be placed at the end of the line

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Missing semicolon
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string);
}
bench.end(n);
}
74 changes: 16 additions & 58 deletions benchmark/buffers/buffer-write-string.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,67 +2,25 @@

const common = require('../common.js');
const bench = common.createBenchmark(main, {
encoding: [
'', 'utf8', 'ascii', 'hex', 'utf16le', 'latin1',
],
args: [ '', 'offset', 'offset+length' ],
len: [2048],
encoding: [ '', 'utf8', 'ascii' ],
len: [0, 1, 8, 16, 32],
n: [1e6],
});

function main({ len, n, encoding, args }) {
let string;
let start = 0;
function main({ len, n, encoding }) {
const buf = Buffer.allocUnsafe(len);

switch (args) {
case 'offset':
string = 'a'.repeat(Math.floor(len / 2));
start = len - string.length;
if (encoding) {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, start, encoding);
}
bench.end(n);
} else {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, start);
}
bench.end(n);
}
break;
case 'offset+length':
string = 'a'.repeat(len);
if (encoding) {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, 0, buf.length, encoding);
}
bench.end(n);
} else {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, 0, buf.length);
}
bench.end(n);
}
break;
default:
string = 'a'.repeat(len);
if (encoding) {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, encoding);
}
bench.end(n);
} else {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string);
}
bench.end(n);
}
const string = 'a'.repeat(len);
if (encoding) {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string, encoding);
}
bench.end(n);
} else {
bench.start();
for (let i = 0; i < n; ++i) {
buf.write(string);
}
bench.end(n);
}
}
27 changes: 24 additions & 3 deletions lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1082,10 +1082,10 @@ function _fill(buf, value, offset, end, encoding) {
Buffer.prototype.write = function write(string, offset, length, encoding) {
// Buffer#write(string);
if (offset === undefined) {
return this.utf8Write(string, 0, this.length);
}
offset = 0;
length = this.length;
// Buffer#write(string, encoding)
if (length === undefined && typeof offset === 'string') {
} else if (length === undefined && typeof offset === 'string') {
encoding = offset;
length = this.length;
offset = 0;
Expand All @@ -1108,6 +1108,27 @@ Buffer.prototype.write = function write(string, offset, length, encoding) {
}
}

const len = string?.length;
if (
len <= 16 &&
len <= length &&
(!encoding || encoding === 'ascii' || encoding === 'utf8') &&
typeof string === 'string'
) {
for (let n = 0; true; n++) {
if (n === len) {
return len;
}

const code = StringPrototypeCharCodeAt(string, n);
if (code >= 128) {
break;
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@lpinca lpinca Aug 11, 2024 •
edited
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I think that buffer.write('aaaaa€') now returns 3 instead of 8.

Edit: I think it is just slower now.

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Based on?

buffers/buffer-write-string.js n=1000000 len=1 args='' encoding=''         ***    526.57 %      ±36.19% ±51.92% ±76.21%
buffers/buffer-write-string.js n=1000000 len=16 args='' encoding=''        ***     52.39 %      ±18.12% ±25.97% ±38.06%
buffers/buffer-write-string.js n=1000000 len=32 args='' encoding=''                -3.44 %      ±10.55% ±14.63% ±20.33%
buffers/buffer-write-string.js n=1000000 len=8 args='' encoding=''         ***    196.38 %       ±3.09%  ±4.43%  ±6.49%

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@lpinca lpinca Aug 11, 2024 •
edited
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It seems that the benchmark does not use a string with mixed sigle byte and multibyte characters. I think the worst case would be something like this 'a'.repeat(15) + '€'. In this case the optimization is only overhead.

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Yes. We're trying to optimize for the most common case.

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@lpinca lpinca Aug 11, 2024 •
edited
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Is an ASCII only string whose length is less than or equal to 16 characters the most common case?

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Regression is minimal for non one byte case:

buffers/buffer-write-string-short.js n=1000000 char='€' len=0         ***    606.09 %      ±26.40% ±36.19% ±49.34%
buffers/buffer-write-string-short.js n=1000000 char='€' len=1                 -0.45 %      ±13.79% ±19.68% ±28.63%
buffers/buffer-write-string-short.js n=1000000 char='€' len=16                -0.76 %       ±5.97%  ±8.50% ±12.32%
buffers/buffer-write-string-short.js n=1000000 char='€' len=32                 0.51 %      ±11.84% ±16.61% ±23.50%
buffers/buffer-write-string-short.js n=1000000 char='€' len=8           *     -8.12 %       ±6.90%  ±9.87% ±14.43%
buffers/buffer-write-string-short.js n=1000000 char='a' len=0         ***    543.24 %      ±12.04% ±17.27% ±25.35%
buffers/buffer-write-string-short.js n=1000000 char='a' len=1         ***    478.53 %      ±31.70% ±45.53% ±66.96%
buffers/buffer-write-string-short.js n=1000000 char='a' len=16        ***    112.38 %       ±6.11%  ±8.72% ±12.69%
buffers/buffer-write-string-short.js n=1000000 char='a' len=32         **     -5.18 %       ±3.21%  ±4.57%  ±6.64%
buffers/buffer-write-string-short.js n=1000000 char='a' len=8         ***    218.82 %      ±11.24% ±15.64% ±21.85%

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https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1597/

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@ronag ronag Aug 11, 2024 •
edited
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Better comparison:

                                                                  confidence improvement accuracy (*)     (**)    (***)
buffers/buffer-write-string-short.js n=1000000 fallback=0 len=0         ***    555.83 %      ±10.01%  ±14.34%  ±21.00%
buffers/buffer-write-string-short.js n=1000000 fallback=0 len=1         ***    447.19 %     ±126.93% ±182.34% ±268.25%
buffers/buffer-write-string-short.js n=1000000 fallback=0 len=16        ***    118.07 %      ±18.44%  ±26.17%  ±37.74%
buffers/buffer-write-string-short.js n=1000000 fallback=0 len=32                -1.22 %       ±5.77%   ±8.22%  ±11.92%
buffers/buffer-write-string-short.js n=1000000 fallback=0 len=8         ***    192.61 %      ±38.32%  ±54.53%  ±78.97%
buffers/buffer-write-string-short.js n=1000000 fallback=1 len=0         ***    522.42 %     ±106.34% ±152.67% ±224.38%
buffers/buffer-write-string-short.js n=1000000 fallback=1 len=1          **     -4.23 %       ±3.03%   ±4.21%   ±5.85%
buffers/buffer-write-string-short.js n=1000000 fallback=1 len=16        ***    -24.35 %       ±9.58%  ±13.18%  ±18.07%
buffers/buffer-write-string-short.js n=1000000 fallback=1 len=32                -4.96 %      ±12.35%  ±17.52%  ±25.26%
buffers/buffer-write-string-short.js n=1000000 fallback=1 len=8         ***    -22.52 %       ±7.75%  ±11.02%  ±15.95%

@mcollina @anonrig wdyt?

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It does not make much sense to benchmark length 0 and 1 imho. I'm also not convinced that length <= 16 is a common case, but I have no proof (so far, there is only one comment with less 16 bytes in the PR comments).

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We use it a lot for primary keys that usually are less than 16 bytes. Also for building e.g. json responses require writing lots of small strings.

}

this[offset + n] = code;
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}
}

if (!encoding)
return this.utf8Write(string, offset, length);

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