&quot;Good performance&quot; needs to be on par or better with any userspace RNG. It&#x27;s great if it&#x27;s better but as long as there&#x27;s an implementation that is on par with userspace there&#x27;s no reason to write userspace RNGs at least from the performance perspective.<p>Though there will still be people doing it for various reasons, one of them &quot;because we can&quot;.