7M keys hash and GC hiccups

keys.js

// 2012-05-19 jorge@jorgechamorro.com

var o;
function boot () {
  o= {};
  var i= 7e6;
  while (i--) {
    var key= i.toString(36);
    o[key]= { id:key };
  }
}

function rnd (x) { return Math.floor(Math.random()*x) }

function touchSingleThread () {
  keysCtr++;
  var key= rnd(7e6).toString(36);
  o[key]= {id:key};
  process.stdout.write(' '+ key);
  process.nextTick(touchSingleThread);
}

function touchMultiThread () {
  var key= rnd(7e6).toString(36);
  var cmd= 'o["'+ key+ '"]= {id:"'+ key+ '"};"'+ key+ '";';
  thread.eval(cmd, cb);
}

function cb (err, key) {
  keysCtr++;
  process.stdout.write(' '+ key);
  process.nextTick(touchMultiThread);
}

function loop () {
  if ((++loopsCtr % 1e3) === 0) dspRates();
  process.nextTick(loop);
}

function dspRates () {
  var now= Date.now();
  var str= "\n\n\n***** Event loop ticks per second -> "+ Math.floor(loopsCtr*1e3/((now- t0) || 1));
  str+= ", keys per second -> "+ Math.floor(keysCtr*1e3/((now- t0) || 1))+ "\n\n";
  console.log(str);
}

var loopsCtr= 0;
var keysCtr= 0;
var t0;
if (process.argv.length > 2) {
  console.log("Multi thread");
  var thread= require('threads_a_gogo').create().eval(boot).eval('boot()', function () {
    t0= Date.now();
    loop();
    touchMultiThread();
  });
  
}
else {
  console.log("Single thread");
  boot();
  t0= Date.now();
  loop();
  touchSingleThread();
}