socket.io memoryUsage profile with heatbeat by manually gc

test.js

var io = require('socket.io').listen(8081);
var parser = require('socket.io').parser;
io.sockets.on('connection', function(socket) {
  var pre;
  var i = 0;
  io.transports[socket.id].parser.on('data', function(p) {
    var packet = parser.decodePacket(p);
    if(packet.type === 'heartbeat') {
      if(global.gc) global.gc();
      var memoryUsage = process.memoryUsage();
      if(!pre) pre = memoryUsage;
      var rss = memoryUsage.rss;
      var heapTotal = memoryUsage.heapTotal;
      var heapUsed = memoryUsage.heapUsed;
      if (i%600 === 0) {
        var delta = {};
        delta['rss'] = rss-pre.rss;
        delta['heapTotal'] = heapTotal-pre.heapTotal;
        delta['heapUsed'] = heapUsed-pre.heapUsed;
        console.log(i, memoryUsage, 'delta:', delta );
        pre = memoryUsage;
      }
      ++i;
    }
  });
  console.log('client connected');
  socket.on('disconnect', function() {
    console.log('client disconnected');
  });
});
io.configure('development', function() {
  io.set('heartbeat interval', 0.1);
  io.set('log level', 0);
});