Using all machine or pc

gistfile1.js

var cluster = require('cluster');
var http = require('http');
var free = 250000000;
var sizeWoker = 157286400;
var NumberWorkers = Math.round( ( os.freemem() - free ) / sizeWoker );

if (cluster.isMaster) {
  for (var i = 0; i < NumberWorkers; i++) {
    cluster.fork();
  }

  cluster.on('exit', function(worker, code, signal) {
    console.log('worker ' + worker.process.pid + ' died');
    cluster.fork();
  });
} else {
  http.createServer(function(req, res) {
    res.writeHead(200);
    res.end("hello world\n");
  }).listen(8000);
}