Unix foundations

The proc

• Process table
• Id
• Location of the kernel address map for the u area
• Current process state
• Forward and backward pointers in scheduled queue
• Sleep channel (7.2.3)
• Scheduling priority and related (Chapter 5)
• Signal handling info(Chapter 4).
• MM info
• Pointers to link active, free, zombie processes in lists
• Flags
• Pointers to keep structures on a hash queue by PID
• Hierarchy info

A typical process hierarchy in 4.3BSD UNIX

• Process ID

• Parent Process ID

• pointer to parent’s proc

• Pointer to the oldest child

• Pointer to the younger sibling

Typical Functions of an Operating-System Kernel

• Process Management
• Process creation and termination
• Process scheduling and dispatching
• Process switching
• Process synchronization and support for inter-process communication
• Management of process control blocks
• Memory Management
• Allocation of address space to processes
• Swapping
• Page and segment management

Typical Functions of an Operating-System Kernel

• I/O Management
• Buffer management
• Allocation of I/O channels and devices to processes
• Support Functions
• Interrupt handling
• Accounting
• Monitoring

Operating System Control Structures

• An OS maintains the following tables for managing processes and resources:
• Memory tables
• I/O tables
• File tables
• Process tables

Memory Tables

• Allocation of main memory to processes
• Allocation of secondary memory to processes
• Protection attributes for access to shared memory regions
• Information needed to manage virtual memory