leaking memory?

gistfile1.js

var http = require('http')
    , util = require('util')
    , pwd = '/Users/victor/Downloads/images'
    , fs = require('fs')
    , mfds = 1024 // max open file descritors
    , ofds = 0
    , memwatch = require('memwatch')
    , _ = require('underscore')

function copyFiles(){
    fs.readdir(pwd,function(err,files){
        if(err) throw err;
        var filename = ''
        
        while(ofds < mfds) addStream();
        function addStream(){
            if(files.length==0) return done();
            filename = files.pop();
            var wstream = fs.createWriteStream('/dev/null')
                , rstream = fs.createReadStream(pwd + '/' + filename)
            ofds+=2;
            var after = _.after(2,function(){
                wstream = null;
                rstream = null;
                ofds-=2;
                addStream();
            });
            rstream.on('close',after);
            wstream.on('close',after);
            rstream.pipe(wstream);
        }
        function done(){
            if(ofds===0){
                files = null;
                filename = null;
                process.stdout.write('DONE!');
                memwatch.gc();
                process.nextTick(copyFiles);
            }
        }
    });
}
setTimeout(copyFiles,1000);

var hd = new memwatch.HeapDiff();

// report to console postgc heap size
memwatch.on('stats', function(d) {
    console.log("postgc: current_base: %s",d.current_base);
    // Take the second snapshot and compute the diff
    var diff = hd.end();
    console.log(util.inspect(diff.after.size,true,10));
    hd = new memwatch.HeapDiff();
});

memwatch.on('leak', function(d) {
    console.log("LEAK:", d);
    throw new Error('leak detected');
});

// also report periodic heap size (every 10s)
setInterval(function() {
    console.log("heap: %s",process.memoryUsage().heapUsed);
},5000);

it turns out this is a bug in memwatch not node :P