sampling-heap-test.js

const heapProfile = require('heap-profile');
heapProfile.start({sampleIntervalBytes: 32 * 1024, stackDepth: 128});

function totalHeapSize(n) {
  let size = 0;
  for (let a of n.allocations) {
    size += a.size * a.count;
  }
  for (let ch of n.children) {
    size += totalHeapSize(ch);
  }
  return size;
}

let rss = 0;
let heapTotal = 0;
let heapUsed = 0;
let heapUsedProfiler = 0;
let numProfiles = 0;
setInterval(() => {
  let mu = process.memoryUsage();
  rss = mu.rss;
  heapTotal = mu.heapTotal;
  heapUsed = mu.heapUsed;
  heapUsedProfiler = totalHeapSize(heapProfile.get());
  numProfiles++;
}, 10);

setInterval(() => {
  console.log(
      'rss',
      (rss / (1024 * 1024)).toFixed(3),
      'MiB,',
      'heap total',
      (heapTotal / (1024 * 1024)).toFixed(3),
      'MiB,',
      'heap used',
      (heapUsed / (1024 * 1024)).toFixed(3),
      'MiB,',
      'heap used (profiler)',
      (heapUsedProfiler / (1024 * 1024)).toFixed(3),
      'MiB,',
      'profile count',
      numProfiles,
  );
}, 2000);

// Make 2**depth allocations of size bytes each, at different stacks.
// Returns the array of made allocations.
function allocate(size, depth) {
  if (depth == 0) {
    return [new Int8Array(size)];
  }
  return allocate(size, depth-1).concat(allocate2(size, depth-1));
}
function allocate2(size, depth) {
  if (depth == 0) {
    return [new Int8Array(size)];
  }
  return allocate(size, depth-1).concat(allocate2(size, depth-1));
}

// Intentionally global to prevent GC.
let ref = [];

let mode = process.argv[2];
if (mode === 'loopalloc') {
  setInterval(() => {
    if (ref.length > 16) {
      ref[15] = null;
      ref.shift();
    }
    ref.push(allocate(128, 16)); // 128 bytes * 2**16 = 2**23 bytes = 8 MiB
  }, 1000);
} else if (mode === 'expressapp') {
  const express = require('express')
  const app = express()
  const http = require('http');

  app.get('/', (req, res) => res.send('Hello World!'));

  app.listen(3000, () => {
    console.log('Express app listening on port 3000...');
    // Simulate some server load.
    setInterval(() => {
      http.get('http://localhost:3000/', (resp) => {
      }).on("error", (err) => {
        console.log("Error: " + err.message);
      });
    }, 1);
  });
} else {
  throw new Error('Expected "loopalloc" or "expressapp", got "' + mode + '"');
}