vm_allocate

1. User Processcall Kernel with vm_allocate()
   • Kernelcall Pager about page initialization
   • User Process meets page fault interrupt
   • Kernel request Pager
   • Pager provide page
   • Kernel resumes User Process

IPC

• task, thread, port, message
• the concept of thread at time ensure the ability of concurrency

port

• likes FDs, each process has a port table
• representing each endpoint of a two-way IPC
• system call
  1. ask the kernel for access to a port
     • use IPC to send messages to that port
• model on UNIX file system concepts

Virtual Memory

• copy-on-write starts from here

Mach 3

• Mach becomes independent from BSD
• SO SLOW. a simple Unix system call would refer to tens of port, permission setting, message passing

deficiencies

• kernel check every message for validity
• additional privileges would be granted to user-space programs
• overhead of IPC
• kernel has no clue about memory paging
• Mach bases on mapping memory around between programs, any “cache miss” made IPC calls slow

Reviews

Notes