Inside Cisco IOS Software Architecture (CCIE Professional Development)

IOS Processes

IOS processes are essentially equivalent to a single thread in other operating systems—IOS processes have one and only one thread each. Each process has its own stack space, its own CPU context, and can control such resources as memory and a console device (more about that later). To minimize overhead, IOS does not employ virtual memory protection between processes. No memory management is performed during context switches. As a result, although each process receives its own memory allocation, other processes can freely access that same memory.

IOS uses a priority run-to-completion model for executing processes. Initially, it might appear that this non-preemptive model is a poor choice for an operating system that must process ...