operating system organization

Operating Systems: A Modern Perspective, Chapter 3

Slide 3-1

Copyright © 2004 Pearson Education, Inc.


Slide 3-2


3Operating SystemOrganization


Slide 3-3


Purpose of an OS

The Abstractions

Create the Abstractions

Coordinate Useof the AbstractionsProcesses


Slide 3-4


OS Requirements

• Provide resource abstractions– Process abstraction of CPU/memory use

• Address space

• Thread abstraction of CPU within address space

– Resource abstraction• “Anything a process can request that can block the

process if it is unavailable”

• NT uses “object abstraction” to reference resources

– File abstraction of secondary storage use


Slide 3-5


DOS -- Resource Abstraction Only

Processor(s) Main Memory Devices

ProgramProgram

ProgramProgram

ProgramProgram

OS ServicesOS Services

LibrariesLibraries

ROM RoutinesROM Routines


Slide 3-6


OS Requirements (cont)

• Provide resource abstractions

• Manage resource sharing– Time/space-multiplexing– Exclusive use of a resource– Isolation– Managed sharing


Slide 3-7


Abstraction & Sharing


LibrariesLibraries

ROM RoutinesROM Routines

ProgramProgramStateState

Process


Process


Process

OS Services • Abstraction• Manage sharing


Slide 3-8


OS Design Constraints

• Performance

• Protection and security

• Correctness

• Maintainability

• Commercial factors

• Standards and open systems


Slide 3-9


Performance

• The OS is an overhead function should not use too much of machine’s resources

• Minimum functionality is to implement abstractions

• Additional function must be traded off against performance– DOS: one process– UNIX: low level file system


Slide 3-10


Protection & Security

• Multiprogramming resource sharing

• Therefore, need software-controlled resource isolation

• Security policy: Sharing strategy chosen by computer’s owner

• Protection mechanism: Tool to implement a family of security policies


Slide 3-11


Correctness & Maintainability

• Security depends on correct operation of software trusted vs untrusted software

• Maintainability relates to ability of software to be changed

• If either is sufficiently important, can limit the function of the OS– Guiding a manned spaceship– Managing a nuclear reactor


Slide 3-12


Device Management

Device-IndependentPart

Device-IndependentPart

Device-DependentPart


Device …Device Device






Slide 3-13


Process, Thread, and Resource Management

…Processor

PrimaryMemory

AbstractResources

MultiprogrammingMultiprogramming

ThreadAbstraction

ThreadAbstraction

ProcessAbstraction

ProcessAbstraction Generic

ResourceManager

GenericResourceManager

OtherOther


Slide 3-14


Memory Management

PrimaryMemory

ProcessManager

ProcessManager

BlockAllocation

BlockAllocation

VirtualMemory

VirtualMemory

Isolation &Sharing

Isolation &Sharing

StorageDevices


Slide 3-15


Exclusive Access to a Resource

Process AProcess A

SupervisorProgram

SupervisorProgram

A’s ProtectedObject

A’s ProtectedObject

Processor

Process BProcess B


Slide 3-16


Processor Modes

• Mode bit: Supervisor or User mode

• Supervisor mode– Can execute all machine instructions– Can reference all memory locations

• User mode– Can only execute a subset of instructions– Can only reference a subset of memory

locations


Slide 3-17


Kernels

• The part of the OS critical to correct operation (trusted software)

• Executes in supervisor mode

• The trap instruction is used to switch from user to supervisor mode, entering the OS


Slide 3-18


Supervisor and User Memory

UserSpace

UserSpace

SupervisorSpace

SupervisorSpace

UserProcess

UserProcess

SupervisorProcess

SupervisorProcess


Slide 3-19


Procedure Call and Message Passing Operating Systems

call(…);

trap

return;

send(…, A, …);receive(…, B, …);

receive(…A, …); …send(…, B, …);

send/receive


Slide 3-20


System Call Using the trap Instruction

…fork();…

fork() {…trap N_SYS_FORK()…}

sys_fork()

sys_fork() {/* system function */ … return;}

KernelTrap Table


Slide 3-21


A Thread Performing a System Call

User Space Kernel Space

fork();

sys_fork() {

}

Thread


Slide 3-22


Basic Operating System Organization


Process, Thread &Resource Manager

MemoryManager

DeviceManager

FileManager


Slide 3-23


LibrariesLibraries CommandsCommands

Device DriverDevice Driver

The UNIX ArchitectureInteractive User

ApplicationPrograms

ApplicationPrograms

OS System Call Interface



Dri

ver

Inte

rfac

eD

rive

r In

terf

ace

…Monolithic Kernel Module•Process Management•Memory Management•File Management•Device Mgmt Infrastructure

Trap Table

…


Slide 3-24


Microkernel Organization

Device DriversDevice DriversMicrokernelMicrokernel


LibrariesLibraries

ProcessProcess

ProcessProcess

ProcessProcess

ServerServer ServerServer ServerServer

User

Supervisor


Slide 3-25


Windows NT Organization


LibrariesLibraries

ProcessProcess

ProcessProcess

ProcessProcess

SubsystemSubsystemUser

Supervisor

SubsystemSubsystem SubsystemSubsystem

Hardware Abstraction LayerHardware Abstraction LayerNT Kernel

NT ExecutiveI/O SubsystemI/O Subsystem

TT

TT

TT T T

T

Process ManagementMemory ManagementFile ManagementDevice Mgmt Infrastructure


Slide 3-26


Monitoring the Kernel


LibrariesLibraries

ProcessProcess

ProcessProcess

ProcessProcess

SubsystemSubsystem SubsystemSubsystem SubsystemSubsystem

Hardware Abstraction LayerHardware Abstraction LayerNT Kernel

NT ExecutiveI/O SubsystemI/O Subsystem

TT

TT

TT T T

TTaskManager

pview

pstat

Supervisor

User

operating system organization

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