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UMD Operating Systems Course by Prof. Hicks (CMSC 412) - Prof. Michael W. Hicks, Study notes of Operating Systems

University of MarylandOperating Systems
Prof. Michael W. Hicks

An overview of the operating systems course offered in the fall 2004 semester at the university of maryland, college park in the cmsc 412 program taught by professor michael hicks. The course covers the fundamentals of operating systems, including resource management, virtual machines, and abstraction. Students will work on projects to build an operating system using the geekos academic operating system and the cyclone programming language. The document also includes information about the course schedule, grading, and required materials.

Typology: Study notes

Pre 2010

Uploaded on 07/30/2009

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CMSC 412
Operating Systems
Fall 2004
Professor Michael Hicks
Welcome!
• Read the Syllabus
– read the warning about the size of the project
– make sure you get the 6th edition (or later) of
the book
• Discussion Sections (start Wednesday)
– focus on the project
– meet only once a week
• Probably we will have three times total per week; you
can attend the section of your choice. See the web
page.
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Download UMD Operating Systems Course by Prof. Hicks (CMSC 412) - Prof. Michael W. Hicks and more Study notes Operating Systems in PDF only on Docsity!

CMSC 412

Operating Systems

Fall 2004 Professor Michael Hicks

Welcome!

  • Read the Syllabus
    • read the warning about the size of the project
    • make sure you get the 6th^ edition (or later) of the book
  • Discussion Sections (start Wednesday)
    • focus on the project
    • meet only once a week
      • Probably we will have three times total per week; you can attend the section of your choice. See the web page.

Projects

  • The best way to understand is by doing
    • So, we will build an operating system that works on bare hardware by extending the GeekOS academic operating system. 6 projects total.
  • Project #0 Handout (posted August 31)
    • It will be due late next week.
    • It will get you familiar with the simulator and the Cyclone programming language, which you can use to write some or all of the project. What is Cyclone? Glad you asked …

Cyclone

  • Based on C
    • Low-level control over memory management, data representation, and access to the machine
  • But type-safe!
    • Rules out many hard-to-find bugs and security holes - Buffer overflows - Dangling pointers
    • These bugs have killed many projects

Class Grades Server

http://grades.cs.umd.edu

  • Get your LinuxLab account from here
    • CS computing cluster. Projects must work and be submitted on these machines.
  • Complete grade information
  • Interface for requesting regrades on exams and projects (with deadline!)

Course Material

• Reading

  • Chapter 1
  • Chapter 2 (for Wednesday)

• Coordination with other section

  • lectures and exams may differ
  • projects will be the same

Why Study OSs?

  • Understand computer systems
    • From the hardware to applications
    • Helpful for understanding performance, security, reliability, and other issues

Why Study OSs?

  • Understand principles of abstraction
    • OSs are large and complex. How do we manage this complexity?
    • Abstraction:
      • Break each piece into self-contained chunks
      • Plug each piece together
    • Different views of service from view of the provider and view of the user
    • These principles will serve you in other software systems projects - E.g., thinking about concurrency

What is an Operating System?

  • Resource Manager
    • Resources include: CPU, memory, disk, network
    • OS allocates and de-allocates these resources
  • Virtual Machine
    • provides an abstraction of a larger (or just different) machine
    • Examples:
      • Virtual memory - looks like more memory
      • Java - pseudo machine that looks like a stack machine
      • IBM VM - a complete virtual machine (can boot multiple copies of an OS on it)
  • Multiplexor
    • allows sharing of resources and protection
    • motivation is cost: consider a $40M supercomputer

What is an OS (cont)?

  • Provider of Services
    • includes most of the things in the above definition
    • provide “common” subroutines for the programmer - windowing systems - memory management
  • The software that is always loaded/running
    • generally refers to the Os kernel.
      • small protected piece of software
  • All of these definitions are correct
    • but not all operating have all of these features

Abstract View of System

Operating System Cousins

  • Hardware
    • OS is managing hardware resources so needs to know about the ugly details of the hardware - interrupt vectors - page tables - I/O registers
    • some features can be implemented either in hardware or the OS
  • Languages
    • can you write an OS in any language?
      • No: need to be able to explicitly layout data structures to match hardware

Multiprogramming

  • Many jobs active “at once”
    • Each job no longer runs to completion before the next can start
    • Many jobs resident in memory at once; the CPU is shared between them
  • Job scheduling
    • which jobs to load into memory

Multiprogramming OSs

  • Must manage resources
    • Memory
    • I/O devices
    • CPU
    • Want to be fair and efficient
  • CPU scheduling
    • which memory-resident program to run
  • Protection
    • Prevent errant job from tainting results of another

Multitasking (Timesharing)

  • Like multiprogramming, but interactive
    • Switching between tasks is very fast
  • Preemption: interrupting a job to transfer control to another job - Quantum: the time slice allocated to a process before it’s preempted. Modern OS typically 50 ms.
  • Interactivity requires more support
    • Filesystem, virtual memory, synchronization, deadlock avoidance

Desktop System

  • Catered to a single user
  • Goal: flexibility and responsiveness
    • Support interactive I/O devices
    • May not need to be as efficient as multi- user OS to be more responsive
    • May be less concerned with protection

Real-time Systems

  • Control device in a dedicated application - Medical imaging, industrial control, etc.
  • Well-defined fixed time constraints
  • Variants
    • Hard: can never miss a deadline
    • Soft: less stringent. Thus permits unpredictable elements like caches, disks, etc.

Handheld Systems

  • PDAs, cell phones, etc.
  • Issues
    • Limited memory
    • Slow (power-constrained) processors
    • Small display

Migration of OS features

OS Goals: Usability

  • Robustness
    • accept all valid input
    • detect and gracefully handle all invalid input
    • should not be possible to crash the OS
  • Consistency
    • same operation should mean the same thing
      • read from a file or a network should look the same
      • a “-” flag should be the same in different commands
    • conventions
      • define the convention
      • follow the convention when adding new items

Adaptability Goals

  • Tailored to the environment
    • server vs. workstation
    • multi-media vs. data entry
  • Changes over time
    • added memory
    • new devices
  • Extensible
    • third parties can add new features
      • database vendors often need custom features
    • end customers can extend the system
      • new devices
      • new policies