If you type `console.log('nocache')` right before the `module.exports.loop` line,you'll see, that cache is not permamemt.It means, that the code outside of `module.exports.loop` method (including all your `require()` calls) is executed occasionly.As far as each `require()` call is *CPU-heavy*, you do have that spikes at start sometimes.
In the presence of cpu spikes, you may want to get know the real 'used cpu' value, that can be compared to your 'cpu limit'. So, you may calculate script's execution time average, let us say: for the last 30 ticks. At least it works fine for me.