Nucleus

Overview

• Goal: to suit diverse requirements of program scheduling and resource allocation.
• A fundamental set of primitives allows the dynamic creation and control of a hierarchy of processes as well as the communication among them.
• Micro kernel

3 parts of the nucleus

1. Processes
2. Processes Communication

3. Process Hierarchy

4. Parent process can start, stop, remove its own children.

5. External process

   • About the device (I/O…)

6. Peripheral -- device

   • Document -- file/data

Process Commnunication (internal processes)

• Nucleus administers a common pool of message buffering and a message queue for each process.
• send message (receiver, message, buffer),
• wait message (sender, message, buffer),
  • delays the requesting procee until an message arrives in its queue.
• send answer (result, answer, buffer),
• wait answer (result, answer, buffer)
  • delays the requesting procee until an answer arrives in a given buffer.

Synchronization

• Message Passing

  • Message passing is key to some models of concurrency and object-oriented programming.

• Pros: don't mess up with each other.

• Cons: less efficient (need to copy and copy)