MessagePack slower than native node.js JSON

I just installed node-msgpack and tested it against native JSON. MessagePack is much slower. Anyone know why?

Using the authors' own benchmark...

node ~/node_modules/msgpack/bench.js 
msgpack pack:   4165 ms
msgpack unpack: 1589 ms
json    pack:   1352 ms
json    unpack: 761 ms

I'll assume you're talking about https://github.com/pgriess/node-msgpack.

Just looking at the source, I'm not sure how it could be. For example in src/msgpack.cc they have the following:

Buffer *bp = Buffer::New(sb._sbuf.size);
memcpy(Buffer::Data(bp), sb._sbuf.data, sb._sbuf.size);

In node terms, they are allocating and filling a new SlowBuffer for every request. You can benchmark the allocation part by doing following:

var msgpack = require('msgpack');
var SB = require('buffer').SlowBuffer;
var tmpl = {'abcdef' : 1, 'qqq' : 13, '19' : [1, 2, 3, 4]};

console.time('SlowBuffer');
for (var i = 0; i < 1e6; i++)
    // 20 is the resulting size of their "DATA_TEMPLATE"
    new SB(20);
console.timeEnd('SlowBuffer');

console.time('msgpack.pack');
for (var i = 0; i < 1e6; i++)
    msgpack.pack(tmpl);
console.timeEnd('msgpack.pack');

console.time('stringify');
for (var i = 0; i < 1e6; i++)
    JSON.stringify(tmpl);
console.timeEnd('stringify');

// result - SlowBuffer: 915ms
// result - msgpack.pack: 5144ms
// result - stringify: 1524ms

So by just allocating memory for the message they've already spent 60% of stringify time. There's just one reason why it's so much slower.

Also take into account that JSON.stringify has gotten a lot of love from Google. It's highly optimized and would be difficult to beat.