Process Memory Layout and Elements Quiz

Process Creation

• Child process: a new process created by an existing process
• Process spawning: when the OS creates a process at the explicit request of another process

Process Termination

• Reasons for process termination:
  • Normal completion
  • Time limit exceeded
  • Memory unavailable
  • Bounds violation
  • I/O failure
  • Invalid/Privileged instruction
  • Parent termination/request

Process States

• New: the process is being created
• Ready: the process is waiting to be assigned to a processor
• Running: instructions are being executed
• Waiting/Blocked: the process is waiting for some events to occur
• Terminated/Exit: the process has finished execution

Process State Transition Diagram with Suspend States

• Swapping: when none of the processes in main memory is in the Ready state, the OS swaps one of the blocked processes out on to disk into a suspend queue

Processes Resource Ownership

• A process includes a virtual address space to hold the process image
• The OS performs a protection function to prevent unwanted interference between processes with respect to resources

Process Execution

• A process follows an execution path that may be interleaved with other processes
• A process has an execution state (Running, Ready, etc.) and a dispatching priority and is scheduled and dispatched by the OS

Dual-Core Design

• A CPU that has two processing units in one integrated circuit
• Cores work simultaneously to achieve a much faster operating speed
• Cores can handle tasks simultaneously because each core has its own cache memory and controller

Computer-System Architecture

• Most systems use a single general-purpose processor
• Multiprocessors systems are growing in use and importance
• Also known as parallel systems, tightly-coupled systems
• Advantages include increasing throughput
• Two types of multiprocessors:
  • Asymmetric Multiprocessing: processors are not treated equally, master-slave approach
  • Symmetric Multiprocessing: all processors are treated equally, shared memory approach

Operating System Structure

• Multiprogramming (Batch system): OS switches to another job when current job needs to wait
• Time sharing (Multitasking system): switching happens when allowed time expires or where there is another reason for current process to wait

Interrupts

• Problem: I/O devices are slower than the processor, causing wasted processor time
• Solution: interrupts allow different modules to interrupt the normal sequencing of the processor

Process Memory Layout

• Text section containing program code
• Data section containing global variables
• Heap containing memory dynamically allocated during run-time

Process Elements

• Process Control Block (PCB) contains elements that characterize a process
• Elements include:
  • Identifier: used to differentiate between processes
  • State: identifies what the process is being used for
  • Priority: OS processes with high priority must execute first
  • Program counter: the address of the next instruction
  • Memory pointers: start and end memory locations of a process
  • Context data: represent the registers’ values used in the process
  • I/O status information: the status of the required I/O operations needed for the process
  • Accounting information: includes CPU time, memory size used, the time for resources

Process Terminologies

• Trace: the behavior of an individual process by listing the sequence of instructions that execute
• Dispatcher: a small program that switches the processor from one process to another