Something wrong with the implementation of the "promise.then"

[Daeren]

Win 7 x64 | Node.js v4.2.1

Code:

var t = 1000 * 1000 * 1;

function fCookie(x, z) {
    return new Promise(resolve => resolve(x + z));
}

console.time("#1 | Promise");
while(t--) fCookie(1, 3).then(function(r) {});
console.timeEnd("#1 | Promise");

Results:

//-] Without: ".then"
//>  1m - 400ms - 20Mb RAM (nodejs Promise)
//>  1m - 300ms - 15Mb RAM (bluebird Promise)

//-] With: ".then"
//>  1m - 4899ms - 1.1Gb RAM (nodejs Promise) ~ (4x | 3x)
//>  1m - 1255ms - 370Mb RAM (bluebird Promise)

So a lot of memory, so slow ...

[thefourtheye]

Most likely a v8 thing, as Node.js uses underlying v8's Promise implementation.

[benjamingr]

Yes, native promises are slower and consume more memory than bluebird promises, this is a well known fact. I think the issue can be closed.

[Trott]

According to this from the v8 mailing list:

This is a known problem. Several reasons:

1. V8 promises haven't been optimised at all. It's on our agenda once our ES6 support is feature complete.
2. V8 promises support various callback hooks into devtools, which cause a certain overhead.
3. Alternative promise implementations tend to take shortcuts relative to the official ES6 semantics (e.g., goog.Promise.all you use below does not support subclassing correctly).

We assume that (1) is the main factor, and will go away eventually, but due to the others some (hopefully minor) differences might remain.

If you have further questions/concerns, I would recommend participating over there. (Promises aren't in Node core. They're supplied by v8.)