fs: improve fsPromises writeFile performance

[Linkgoron]

Currently the writeFile in fs/promises is around three times slower than the non-promisifed version (at least, when I tested various files on my machine). The reason, I believe, is mainly because of chunking, which does not exist at all in the regular version (see writeAll in fs.js) , and is rather small (IMO) in writeFile.

I've increased kWriteFileMaxChunkSize from 2**14 to 512*1024, which is the same as the read buffer size in read_file_context in #37608. This made both writeFile methods essentially the same (the fs/promises is slightly slower in my testing).

It might be correct to also add chunking to the fs version, similar to readFile (#17054 and #25741) - but I believe that should be a different issue with more discussion.

edit:
second commit contains fs.promises.writeFile benchmark

[benjamingr]

@nodejs/fs

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36481/

[benjamingr]

Did you run benchmarks? (Want me to run a benchmark CI?)

[Linkgoron]

Did you run benchmarks? (Want me to run a benchmark CI?)

Sure

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36482/

[benjamingr]

https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/956/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36485/

[Linkgoron]

Did you run benchmarks? (Want me to run a benchmark CI?)

@benjamingr I created a benchmark from joining together readFile and the stream write benchmarks and these are the results:

                                                                                 confidence improvement accuracy (*)    (**)    (***)
fs/writefile-promises.jsconcurrent=1 size=1024 encodingType='asc' duration=5                     3.15 %      ±19.65% ±28.76%  ±43.63%
fs/writefile-promises.jsconcurrent=1 size=1024 encodingType='buf' duration=5                    -1.45 %      ±19.00% ±27.76%  ±42.01%
fs/writefile-promises.jsconcurrent=1 size=1024 encodingType='utf' duration=5                    -4.50 %      ±20.89% ±30.43%  ±45.79%
fs/writefile-promises.jsconcurrent=1 size=1048576 encodingType='asc' duration=5         ***    173.22 %      ±25.84% ±37.82%  ±57.35%
fs/writefile-promises.jsconcurrent=1 size=1048576 encodingType='buf' duration=5         ***    231.60 %      ±47.34% ±75.50% ±132.23%
fs/writefile-promises.jsconcurrent=1 size=1048576 encodingType='utf' duration=5         ***     96.32 %      ±23.32% ±36.83%  ±63.46%
fs/writefile-promises.jsconcurrent=1 size=2 encodingType='asc' duration=5                       -0.32 %      ±12.37% ±19.07%  ±31.57%
fs/writefile-promises.jsconcurrent=1 size=2 encodingType='buf' duration=5                       -1.33 %      ±20.94% ±30.64%  ±46.48%
fs/writefile-promises.jsconcurrent=1 size=2 encodingType='utf' duration=5                       16.01 %      ±18.94% ±30.52%  ±54.37%
fs/writefile-promises.jsconcurrent=1 size=65535 encodingType='asc' duration=5            **     45.30 %      ±23.17% ±35.47%  ±58.05%
fs/writefile-promises.jsconcurrent=1 size=65535 encodingType='buf' duration=5            **     51.37 %      ±29.33% ±42.96%  ±65.25%
fs/writefile-promises.jsconcurrent=1 size=65535 encodingType='utf' duration=5                   23.80 %      ±26.57% ±40.18%  ±64.34%
fs/writefile-promises.jsconcurrent=10 size=1024 encodingType='asc' duration=5                    1.99 %       ±9.16% ±13.36%  ±20.17%
fs/writefile-promises.jsconcurrent=10 size=1024 encodingType='buf' duration=5                    2.70 %      ±15.26% ±22.37%  ±34.02%
fs/writefile-promises.jsconcurrent=10 size=1024 encodingType='utf' duration=5                   -1.32 %      ±13.43% ±19.58%  ±29.51%
fs/writefile-promises.jsconcurrent=10 size=1048576 encodingType='asc' duration=5        ***    123.02 %      ±18.08% ±26.33%  ±39.60%
fs/writefile-promises.jsconcurrent=10 size=1048576 encodingType='buf' duration=5        ***    117.64 %      ±19.14% ±31.10%  ±56.24%
fs/writefile-promises.jsconcurrent=10 size=1048576 encodingType='utf' duration=5        ***    104.12 %      ±27.19% ±42.65%  ±72.64%
fs/writefile-promises.jsconcurrent=10 size=2 encodingType='asc' duration=5                       1.07 %      ±14.19% ±20.69%  ±31.17%
fs/writefile-promises.jsconcurrent=10 size=2 encodingType='buf' duration=5                      -3.72 %       ±9.64% ±14.08%  ±21.30%
fs/writefile-promises.jsconcurrent=10 size=2 encodingType='utf' duration=5                       0.05 %      ±15.13% ±22.05%  ±33.23%
fs/writefile-promises.jsconcurrent=10 size=65535 encodingType='asc' duration=5           **     48.35 %      ±25.17% ±36.97%  ±56.43%
fs/writefile-promises.jsconcurrent=10 size=65535 encodingType='buf' duration=5          ***     67.93 %      ±21.96% ±32.98%  ±52.26%
fs/writefile-promises.jsconcurrent=10 size=65535 encodingType='utf' duration=5                  21.07 %      ±21.74% ±32.11%  ±49.47%

Note that I only ran this 5 runs instead of 30 because it took a really long time (30 minutes on my machine), but I think that the results are pretty good.

[benjamingr]

@Linkgoron I think it makes sense to commit the benchmark as part of this PR - perhaps as a separate second commit.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36497/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36592/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36611/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36617/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/36621/

[aduh95]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/961/

[Divineloyalty]

node/benchmark/fs/writefile-promises.js

Lines 1 to 66 in a97f01e

	// Call fs.promises.writeFile over and over again really fast.
	// Then see how many times it got called.
	// Yes, this is a silly benchmark. Most benchmarks are silly.
	'use strict';
	const path = require('path');
	const common = require('../common.js');
	const fs = require('fs');
	const assert = require('assert');
	const tmpdir = require('../../test/common/tmpdir');
	tmpdir.refresh();
	const filename = path.resolve(tmpdir.path,
	`.removeme-benchmark-garbage-${process.pid}`);
	let filesWritten = 0;
	const bench = common.createBenchmark(main, {
	duration: [5],
	encodingType: ['buf', 'asc', 'utf'],
	size: [2, 1024, 65535, 1024 * 1024],
	concurrent: [1, 10]
	});
	function main({ encodingType, duration, concurrent, size }) {
	let encoding;
	let chunk;
	switch (encodingType) {
	case 'buf':
	chunk = Buffer.alloc(size, 'b');
	break;
	case 'asc':
	chunk = 'a'.repeat(size);
	encoding = 'ascii';
	break;
	case 'utf':
	chunk = 'ü'.repeat(Math.ceil(size / 2));
	encoding = 'utf8';
	break;
	default:
	throw new Error(`invalid encodingType: ${encodingType}`);
	}
	let writes = 0;
	let benchEnded = false;
	bench.start();
	setTimeout(() => {
	benchEnded = true;
	bench.end(writes);
	for (let i = 0; i < filesWritten; i++) {
	try { fs.unlinkSync(`${filename}-${i}`); } catch { }
	}
	process.exit(0);
	}, duration * 1000);
	function write() {
	fs.promises.writeFile(`${filename}-${filesWritten++}`, chunk, encoding)
	.then(() => afterWrite())
	.catch((err) => afterWrite(err));
	}
	function afterWrite(er) {
	if (er) {
	if (er.code === 'ENOENT') {
	// Only OK if unlinked by the timer from main.
	assert.ok(benchEnded);
	return;
	}