Async filesystem ops vs. OS filesystem cache

stattest.js

var fs = require('fs');

var sMax = 500000;
var sDir = 'teststat';
var sCount = 2;

if (!fs.statSync(sDir)) {
  fs.mkdirSync(sDir, 0700);
  for (var a=0; a < 100; ++a)
    fs.writeFileSync(sDir+'/'+a, 'some text');
}

var sT = Date.now();
for (var aC=0; aC < sCount; ++aC)
  astat(0);

function astat(n) {
  if (n < sMax/sCount) {
    fs.stat(sDir+'/'+Math.floor(Math.random()*100), function(err, stats) {
      if (err) throw err;
      astat(++n);
    });
    return;
  }

  if (--aC === 0) {
    console.log('async '+ (Date.now()-sT) +' ms');
    sT = Date.now();
    sstat(0);
  }
}

function sstat(n) {
  if (n < sMax) {
    var stats = fs.statSync(sDir+'/'+Math.floor(Math.random()*100));
    process.nextTick(function() { sstat(++n) });
    return;
  }
  console.log('sync '+ (Date.now()-sT) +' ms');
}