Right. This is a UNIX/Linux book. It's not how IBM mainframe OSs work, or how QNX works, or how L4 works, or even how the Windows kernel works. There's nothing

Right. This is a UNIX/Linux book. It's not how IBM mainframe OSs work, or how QNX works, or how L4 works, or even how the Windows kernel works. There's nothing wrong with that, but they should say so up front. They wrote "From the user’s perspective, disk reads are usually considered non-blocking because they typically complete quickly." Although if all storage is on solid state disk, you might only lose 40us or so per read.