When my program is waiting to read from a network stream, or from a USB device, it uses 0% CPU and responds instantly when the signal comes in. That is how soft

When my program is waiting to read from a network stream, or from a USB device, it uses 0% CPU and responds instantly when the signal comes in. That is how software should be. Maybe there's cases in the kernel where polling is unavoidable. But polling should happen as little as possible - for the sake of both latency and efficiency. I don't spend much time thinking about the kernel. In userland, polling is almost never necessary. I'd love it if just about all software that manages data that changes over time was written such that downstream consumers can be notified when that data changes. This should be the case for filesystems, databases, message queues, web servers, device lists over USB and so on.