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BeOS, the Be Operating System. Robert Robinson CS 550-1. What Is BeOS?. Coded from scratch 1990: Be, Inc. formed 1996: 1 st public release Ran on Be’s proprietary hardware, BeBox 1997: Be quits the hardware business. BeOS History. 1998: Release 4, the money-maker

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Beos the be operating system

BeOS, the Be Operating System

Robert Robinson

CS 550-1


What is beos
What Is BeOS?

  • Coded from scratch

  • 1990: Be, Inc. formed

  • 1996: 1st public release

    • Ran on Be’s proprietary hardware, BeBox

  • 1997: Be quits the hardware business


Beos history
BeOS History

  • 1998: Release 4, the money-maker

    • Runs on PowerPC, x86, more

  • 2000: Release 5, “the demise”

    • “Personal Edition”; 512MB partition limit

  • 2001: Be bought by Palm, Inc.

  • 2001: BeOS R5.1 leaked to public

  • Today: Haiku (changed from OpenBeOS) and YellowTab


Bfs the be file system
BFS, the Be File System

  • Much of structure borrowed from UNIX

  • Journaling

    • Reduces data loss

    • Eliminates need for scandisk or fsck

  • Rich metadata model

    • Database-like approach to file retrieval


Memory management
Memory Management

  • Memory Model

  • Implementation at the Microkernel level

Figure 3 – BeOS Architecture

<[email protected]>


Memory model
Memory Model

  • Virtual Memory Addresses (mapping dynamic memory)

    • Shared by threads and processes

    • Can be locked into RAM

  • Object-Oriented Design

  • Full Memory Protection

  • Symmetric Multi-Processing (SMP)


Implementation at the microkernel level
Implementation at theMicrokernel Level

  • BeOS Threads and Objects

  • Communication between Threads

    • Message Handling with BLooper

    • Ports (FIFO message repositories)

    • Semaphores (data protected locks)

    • Benaphores (Increased efficiency in data protection)


Internal data structures
Internal Data Structures

  • Structures Used in Process Management

    • Thread creation

    • Thread execution and control

    • Thread termination

  • Structures Used in Memory Management

    • BLooper (Interface between objects & threads)

    • Semaphores, Ports, and Images

  • Structures Used in File Management

    • Bfile

    • Bdirectory


Threads
Threads

  • Multi-threaded Architecture of BeOS

    • Pervasive multi-threading

    • Teams

  • Kinds of Threads

    • Real-time & time-sharing

    • listener and image threads


Cpu scheduler
CPU Scheduler

  • Thread priority numbers: 1-120.

  • Levels 1-99: assigned to time-sharing threads.

  • Levels 100-120: reserved for real-time threads.

  • Time-sharing threads are scheduled according to their priority number and a logarithmic scale of 2.

  • So a thread with a priority number greater by 2 is four times as likely to be chosen to execute.


Cpu scheduler continued
CPU Scheduler (continued)

  • A new time-sharing thread is given the processor after every time quantum (3 milliseconds in BeOS).

  • Execution on multiple processors

  • Time-sharing threads must always yield to real-time threads. This makes BeOS a streamlined OS for media applications requiring real-time performance.


Deadlock
Deadlock

  • Problem: Dropping of messages

    • Solution: Port

  • Problem: Manipulation of data by another process during execution.

    • Solution: Semaphores

  • Problem: Semaphores Slowness

    • Solution: Benaphores



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