That's true but I think the bigger reason is that a single address space makes system calls as cheap as regular function calls, since there is no kernel boundary any more.
Ironically, VxWorks's latest major rev was all about turning memory protection on since overwhelmingly people prefer the performance hit of kernel calls over the heisenbugs that come from stomping on the kernel's code and data structures.
Ironically, VxWorks's latest major rev was all about turning memory protection on since overwhelmingly people prefer the performance hit of kernel calls over the heisenbugs that come from stomping on the kernel's code and data structures.