2.8 Real world

Most operating systems have adopted the process concept, and most processes look similar to xv6’s. Modern operating systems, however, support several threads within a process, to allow a single process to exploit multiple CPUs. Supporting multiple threads in a process involves quite a bit of machinery that xv6 doesn’t have, often including interface changes (e.g., Linux’s clone, a variant of fork), to control which aspects of a process threads share.