try to figure out how often we yield for IO / other callbacks

yielding

function yielding() {
    var stop = false,
        stamp = (new Date()).getTime(),
        count = 0,
        clear;
    
    function tick() {
        if (!stop) {
            count++;
            clear = setImmediate(tick);
        }
    }

    setImmediate(tick);
    return {
        stop: function () {
            var duration = ((new Date()).getTime() - stamp) / 1000.0,
                freq = count / duration;

            stop = true;
            clearImmediate(clear);
            console.log('yielded ' + count + ' times in ' + duration + ' seconds. ' + freq + ' y/s')
        }
    };
}