readFileSync vs readFile benchmark

readFileSync_vs_readFile.js

const fs = require('fs');
const fsp = fs.promises;
const util = require('util');

const readFile = util.promisify(fs.readFile);

fs.writeFileSync('a', 'a');

const attempts = 10000;

function runInCallback(left, cb) {
  fs.readFile('a', () => {
    if (left > 0) {
      runInCallback(left - 1, cb);
    } else {
      cb();
    }
  });
}

(async () => {
  console.time('sync');
  for (let i = 0; i < attempts; i++) {
    fs.readFileSync('a');
  }
  console.timeEnd('sync');

  console.time('async');
  for (let i = 0; i < attempts; i++) {
    await readFile('a');
  }
  console.timeEnd('async');

  console.time('async experimental');
  for (let i = 0; i < attempts; i++) {
    const fh = await fsp.open('a', 'r');
    await fh.close();
  }
  console.timeEnd('async experimental');


  console.time('callback');
  await new Promise(r => runInCallback(attempts, r));
  console.timeEnd('callback');

  console.time('nextTick');
  for (let i = 0; i < attempts; i++) {
    await new Promise(r => setImmediate(r));
  }
  console.timeEnd('nextTick');
})().catch(e => console.log(e));

results.md

Kirill's mac

sync: 350.449ms
async: 914.830ms
callback: 853.446ms
nextTick: 54.225ms

gcp outside kubes (node is too old for fs.promises)

sync: 151.101ms
async: 1480.068ms
callback: 1268.984ms
nextTick: 103.432ms

Faux's desktop

sync: 56.665ms
async: 265.667ms
async experimental: 152.745ms
callback: 234.420ms
nextTick: 27.763ms

pod on dev

sync: 157.621ms
async: 4021.526ms
async experimental: 2219.324ms
callback: 3815.933ms
nextTick: 70.360ms

pod on dev, UV_THREADPOOL_SIZE=1

sync: 175.504ms
async: 1856.070ms
async experimental: 1047.297ms
callback: 1793.691ms
nextTick: 78.269ms

pod on dev, UV_THREADPOOL_SIZE=1, taskset -c 1

sync: 145.509ms
async: 849.236ms
async experimental: 593.194ms
callback: 648.267ms
nextTick: 95.132ms

fau.xxx (2011 xeon, rotary discs)

sync: 85.945ms
async: 467.870ms
async experimental: 265.956ms
callback: 444.904ms
nextTick: 34.292ms