I'd like all buffers to be flushed whenever the systemwide CPU becomes idle.

Buffering generally is a CPU-saving technique. If we had infinite CPU, all buffers would be 1 byte. Buffers are a way of collecting together data to process in a batch for efficiency.

However, when the CPU becomes idle, we shouldn't have any work "waiting to be done". As soon as the kernel scheduler becomes idle, all processes should be sent a "flush your buffers" signal.

An interesting idea! Sending signals to all processes sounds expensive as hell though. All that work just to make a system call again to flush a buffer. Maybe a mechanism can be added to make the kernel aware of the user space buffer so it can directly fetch stuff from there when it's idle? Is it kind of like io_uring https://man7.org/linux/man-pages/man3/io_uring_register_buff...

That's a neat idea, probably not all at once though. And it could reduce efficiency for low power systems to be speculatively waking sleeping processes?