Lecture Notes: Interprocess Communication (IPC)

Introduction

• Topic: Interprocess Communication (IPC)
• Context: Discuss how isolated processes can interact with each other.

Key Concepts

• Process: More than executable code; includes CPU state, memory region, open files, and IO devices.
• Isolation: Processes are isolated by default for safety, but this can hinder cooperation.

Classification of Processes

• Independent Processes: Do not cooperate with other processes.
• Cooperating Processes: Share data and need to coordinate activities.
  • Benefits include computational speedup and modularity.

Interprocess Communication Models

1. Shared Memory

   • Allows processes to share a memory space directly.
   • Privilege Instructions: Enforce isolation by preventing access to other processes' memory.
   • System calls create and attach shared memory regions.
   • Processes manage data structure within shared memory, leading to potential issues like race conditions.

2. Message Passing

   • Alternately allows processes to communicate without sharing address space.
   • Involves sending messages through mechanisms like pipes, sockets, and remote procedure calls.
   • Requires system calls for send and receive operations.
   • Mailbox/Queue: Used by the OS kernel to handle message storage and delivery.

Examples of Shared Memory Use

• Chromium Browser: Uses shared memory for modular tasks in browser, renderer, and plugin processes.
• Other Applications: Include simulation software, game engines, DBMS, and deep learning frameworks.

Examples of Message Passing Use

• Socket Interface: Common in client-server architecture for processes on the same or different machines.
  • Ports/Listening Ports: Used to establish communication links.
  • Processes communicate through ports, not directly.

Advantages and Disadvantages

• Shared Memory
  • Faster communication as it allows direct memory access.
  • Requires careful management to avoid conflicts and race conditions.
• Message Passing
  • Easier for isolated address spaces and remote communication.
  • More complex implementation; system calls are costly.

Conclusion

• Message Passing vs. Shared Memory: Message passing is generally sufficient despite being slower.
• Encouragement to explore further and support through links (e.g., codec Crafters).

Final Note

• IPC is crucial for modern applications, enabling complex system functionality and improving efficiency through cooperation.