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Windows - Operating System - Lecture Slides, Slides of Computer Science

All India Institute of Medical SciencesComputer Science

These are the Lecture Slides of Operating System which includes Environment, Fundamental Goal, Programs, Time Line, User Programs, Versus, Operating System, Running, Symmetric Multiprocessing etc.Key important points are: Windows, Preemptive Multitasking, Security, Reliability, Application Compatibility, Extensibility, Portability, International Language, Layered Architecture, System

Typology: Slides

2012/2013

Uploaded on 03/27/2013

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Ch. 5.6.2, 9.10.1, Ch. 22.1-22.5:
Windows XP
•Preemptive multitasking
•Goals:
–Security, reliability, ease-of-use, Windows & POSIX
application compatibility, high-performance,
extensibility, portability, international language support
– Commercial
•“the layered architecture of the system … makes it
so easy to use” [my italics, p. 783, text]
Docsity.com
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Download Windows - Operating System - Lecture Slides and more Slides Computer Science in PDF only on Docsity!

Ch. 5.6.2, 9.10.1, Ch. 22.1-22.5:

Windows XP

  • Preemptive multitasking
  • Goals:
    • Security, reliability, ease-of-use, Windows & POSIX application compatibility, high-performance, extensibility, portability, international language support
    • Commercial
  • “the layered architecture of the system … makes it

so easy to use” [my italics, p. 783, text]

2

Outline

• A little history

• 22.3: System components

• 22.3.2.2: Threads & CPU scheduling

• 22.3.3.2: Virtual memory

• 22.4: Environmental subsystems

• 22.5: File System: NTFS

4

System Components (Fig. 22.1)

5

System Components - 2

  • Seems a microkernel design, but text does not use this term
  • Microkernel: Executes in protected mode
    • HAL: Hardware abstraction layer (p. 788)
      • Some hardware independence
      • HAL provides memory mapping, configuring I/O buses, setting up DMA, motherboard specific facilities
      • Device drivers (I/O manager) can still work directly with hardware
    • Kernel
      • thread scheduling, interrupt & exception handling, CPU synchronization, power failure recovery
      • Never paged out, never preempted
  • User mode processes
    • Environmental subsystems
      • User mode operating systems (e.g., MS-DOS, OS/2, Win32, POSIX)
      • Logon systems
    • User applications

7

CPU Scheduling - 1

  • Priority-based, preemptive scheduling
  • 32 priority levels; each has a queue of threads
    • Variable class: 0-
    • Real-time: 16-
    • Higher numbers indicate higher priority
  • Scheduler traverses from highest to lowest priority

queues

  • Round robin, combined with priority scheme

8

CPU Scheduling - 2

  • Variation on standard round-robin CPU scheduling
  • When thread’s time quantum runs out
    • Variable class: priority lowered
      • unless already base priority
    • Returned to relevant priority level in queue, in ready state
    • Why lower the thread priority? Are there conditions under which a variable class thread will not have its priority lowered?
  • When variable priority thread released from wait state
    • Dispatcher boosts priority, depending on type of wait
    • High boost:
      • Waiting for keyboard I/O
      • Thread associated with user’s active GUI window
    • Low boost: waiting for disk I/O

Virtual Memory: Section 9.10.

  • Demand paging with clustering
    • Bring in neighboring pages on a page fault: “Prefetching”
  • Max/min working set size per process
    • Processes have initial working set size of 50 frames
  • If a process is at its working set maximum and a page

fault occurs

  • Local page replacement
  • When number of free frames drops below a certain

value

  • Automatic working-set trimming
  • memory manager removes pages from processes until processes at working set minimum
  • FIFO or variation of clock algorithm depending on hardware (p. 363) Docsity.com

11

Page tables: 32 bit Processor

(without PAE)

  • 2-level page tables
  • Each process has a page directory (outer page table)
    • 1024 page-directory entries (PDE’s)
    • Size 4 bytes for each PDE
    • Each PDE points to a page table
  • Page table (inner page table)
    • 1024 page-table entries (PTE’s)
    • Size 4 bytes for each PTE
    • Each PTE points to a 4 KB frame of physical memory
    • Page tables are swapped out to disk when necessary
  • Total size of all page tables, per process: 4 MB

Logical

Address

structure Docsity.com

13

Page tables: Page Table Entries

(PTE’s)

• 20 bits for frame number

• 12 bits remain to describe state of page

  • Accessed or written
  • Caching attributes
  • Access mode
  • Global
  • PTE valid

Ch. 22.4: Windows XP

Environmental Subsystems

  • Some implement user-level operating systems
  • Some implement services crucial to all user-level

operating systems

  • E.g., GUI, security management
  • Win
  • Executes in unprotected mode
  • Provides all keyboard, mouse, graphical display
  • Other environmental subsystems use this
  • Separate processes with own input queues
  • Window manager dispatches input to input queue of appropriate process

16

Client/server model - 1

  • User-level operating systems considered to be

“clients”

  • Kernel considered to be “server”
  • Communication between client and server

provided by message passing

  • “Local procedure call” (LPC) facility
    • like Remote Procedure Calls
  • Message passing within a single computer
  • Used to implement system calls

17

Client/server model - 2

  • Server (e.g., kernel)
    • Publishes a globally visible connection port object
  • Client (e.g., Win32), to obtain services provided

by server

  • Opens a handle to server connection port
    • Sends connection request
  • Server creates channel & returns handle to client
  • Channel: pair of private communication ports
    • Client-to-server messages
    • Server-to-client messages
  • Some specifics dependent on message sizes
  • Small messages (e.g., up to a few hundred

bytes) are copied from sender to receiver

  • Shared memory is used for larger messages Docsity.com

19

NTFS: Files

  • In NTFS a file is not a simple stream of bytes as it

is in some operating systems (e.g., Unix)

  • Rather, files are structured objects comprised of

typed attributes

  • Some types of attributes
    • Conventional data of a file
    • Standard attributes: name, creation time, security descriptor
  • Examples of other uses of these typed attributes
    • Mac file resource fork on a Windows XP file server
    • Thumbnail of an image

20

NTFS: Clusters

• Cluster: Unit of disk allocation

• Allocates sectors on disk in contiguous

groups

  • A number of 512 byte disk sectors (power of

two size)

• Example

  • Cluster size is 4096 bytes with disks > 4GB
  • If the (block) sector size on disk is 512 bytes,

this means each cluster is going to be 8 (blocks)

sectors