Spring Operating System

Summary

• How to Innovate OS
• Object Based vs Procedrual Design
• Spring Approach
  • Nucleus “Microkernel” of Spring
  • Object Invocation Across the Network
• Secure Object Invocation
• Virtual Memory Managment in Spring
  • Memory Object Specific Paging
• Spring System Summary
• Dynamic Client Server Relationship
  • Subcontract

How to Innovate OS

Brand new OS or better implementation of known OS?

Market-place needs

• Large complex server software

In order to maintain legacy software, the Sun Microsystems chose an implementation of an existing OS

Object Based vs Procedrual Design

Objects hide internal state and only expose methods

Spring Approach

• Strong interfaces
  • Open, Flexible, and Extensible

Nucleus “Microkernel” of Spring

Domain = Address space

Threads execute in a particular domain

Doors provide access to domains via handles

Object Invocation Across the Network

Proxies are invisible to client and server

Proxy A: export net handle embedding doorX Proxy B: use net handle to connect nuclei

Secure Object Invocation

Front objects provide security mechanisms

• Outside the scope of Spring OS
• Inside realm of service

Multiple front objects can point to the same underyling object but bind to different doors to enforce different security policies.

Front objects can do things like present one-time references to objects

Virtual Memory Managment in Spring

Break linear address space into regions

Each region points to a memory object

Each memory object may map to files, swap space, etc.

Memory Object Specific Paging

Multiple paging mechanisms can be used for different memory objects

Spring System Summary

• Object oriented kernel
  • nucleus
    • Threads + IPC
  • microkernel
    • nucleus + address space
  • door + door table
    • basis for cross domain calls
  • object invocation and cross machine calls
  • virtual memory management
    • address space object, memory object, external pagers, cached obj

Dynamic Client Server Relationship

Subcontract

Contracts between client and server are defined by IDL

Subcontracts are provided to realize ideal connection between client and server

Implementation of contracts are handled through subcontracts to hide runtime details

• makes client side stub generation simpler