benchmark: port cluster/echo to worker

    $ ./node benchmark/cluster/echo.js
    cluster/echo.js n=100000 sendsPerBroadcast=1 payload="string" workers=1: 33,647.30473442063
    cluster/echo.js n=100000 sendsPerBroadcast=10 payload="string" workers=1: 12,927.907405288383
    cluster/echo.js n=100000 sendsPerBroadcast=1 payload="object" workers=1: 28,496.37373941151
    cluster/echo.js n=100000 sendsPerBroadcast=10 payload="object" workers=1: 8,975.53747186485
    $ ./node --experimental-worker benchmark/worker/echo.js
    worker/echo.js n=100000 sendsPerBroadcast=1 payload="string" workers=1: 88,044.32902365089
    worker/echo.js n=100000 sendsPerBroadcast=10 payload="string" workers=1: 39,873.33697018837
    worker/echo.js n=100000 sendsPerBroadcast=1 payload="object" workers=1: 64,451.29132425621
    worker/echo.js n=100000 sendsPerBroadcast=10 payload="object" workers=1: 22,325.635443739284

Refs: ayojs/ayo#115
Reviewed-By: Anna Henningsen <anna@addaleax.net>

PR-URL: #20876
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>

benchmark/fixtures/echo.worker.js

@@ -0,0 +1,7 @@
+'use strict';
+
+const { parentPort } = require('worker');
+
+parentPort.on('message', (msg) => {
+  parentPort.postMessage(msg);
+});

benchmark/worker/echo.js

@@ -0,0 +1,73 @@
+'use strict';
+
+const common = require('../common.js');
+const path = require('path');
+const bench = common.createBenchmark(main, {
+  workers: [1],
+  payload: ['string', 'object'],
+  sendsPerBroadcast: [1, 10],
+  n: [1e5]
+}, { flags: ['--experimental-worker'] });
+
+const workerPath = path.resolve(__dirname, '..', 'fixtures', 'echo.worker.js');
+
+function main(conf) {
+  const { Worker } = require('worker');
+
+  const n = +conf.n;
+  const workers = +conf.workers;
+  const sends = +conf.sendsPerBroadcast;
+  const expectedPerBroadcast = sends * workers;
+  var payload;
+  var readies = 0;
+  var broadcasts = 0;
+  var msgCount = 0;
+
+  switch (conf.payload) {
+    case 'string':
+      payload = 'hello world!';
+      break;
+    case 'object':
+      payload = { action: 'pewpewpew', powerLevel: 9001 };
+      break;
+    default:
+      throw new Error('Unsupported payload type');
+  }
+
+  const workerObjs = [];
+
+  for (var i = 0; i < workers; ++i) {
+    const worker = new Worker(workerPath);
+    workerObjs.push(worker);
+    worker.on('online', onOnline);
+    worker.on('message', onMessage);
+  }
+
+  function onOnline() {
+    if (++readies === workers) {
+      bench.start();
+      broadcast();
+    }
+  }
+
+  function broadcast() {
+    if (broadcasts++ === n) {
+      bench.end(n);
+      for (const worker of workerObjs) {
+        worker.unref();
+      }
+      return;
+    }
+    for (const worker of workerObjs) {
+      for (var i = 0; i < sends; ++i)
+        worker.postMessage(payload);
+    }
+  }
+
+  function onMessage() {
+    if (++msgCount === expectedPerBroadcast) {
+      msgCount = 0;
+      broadcast();
+    }
+  }
+}