operating systems principles design and implementation ...cs325/osp_01.pdf · os_1 os _2 os _3...

Betriebssysteme ws2000/2001

Prof. H. D. Clausen 1

S 2004 CS325 1

Operating Systems PrinciplesOperating Systems Principles

Design and Implementation Design and Implementation Policies and Mechanisms Policies and Mechanisms

S 2004 CS325 2

Textbook: L.Bic and A.C Shaw: Textbook: L.Bic and A.C Shaw: "Operating Systems Principles""Operating Systems Principles"

Other references:

• A.S. Tanenbaum, „Modern Operating Systems“, Prentice-Hall

• Other references – see web site: cs.nmt.edu/~cs325



S 2004 CS325 3

Simple hardware configurationSimple hardware configuration

control

CPU dataaddress

mainmemory

controller controller

device_1 device_2

IO subsystem

user

S 2004 CS325 4

Typical hardware configurationTypical hardware configuration

CPUmain

memory

controller

device

IOC

controller controller

device

IOC/PPU

controller

device



S 2004 CS325 5

Processor performanceProcessor performance

This chart plots relative performance as measured by the SPECint benchmarks with base of one being a VAX 11/780.

S 2004 CS325 6

Memory costMemory cost

Prices of DRAMs (from 16K bits to 64M bits) over time in 1977 dollars.



S 2004 CS325 7

application supportAPI

CISC

RISC

SysCall

systems programs

kernel programs

driver programsSW

HW

application program

SVC

API

S 2004 CS325 8

Principle of abstractionPrinciple of abstraction

• Higher-level function:– Read( file, logical_block, main_memory )

• Lower-level functions– Calculate position of logical_block on the disk;

– Move Read/Write head to corresponding track;

– Check for „seek“ errors;

– Read physical block;

– Check for „read“ errors;

– Copy block to main_memory;



S 2004 CS325 9

Principle of abstractionPrinciple of abstraction

HW

driver

read

Calc_pos Mov_RWhd

ChckSeekErrChckReadErr

ReadPhysBlk CopyBlkToMem

Functions = “virtual” instructions

machine instructions

basic machine

extended machine

S 2004 CS325 10

“Logical Design”“Logical Design”

• Logical -> “virtual” machine• Real -> “physical” machine

• Design principles –– “policy”, strategy – plan of action --- design

– “mechanism”, tactics, approach --- implementation

• Example: waiting queue– Logical organization: FIFO, priority, some scheduling scheme

– Physical organization: linked list, doubly linked list, circular list, array, heap, …



S 2004 CS325 11

„Timesharing“ „Timesharing“ –– ttime ime sslicinglicing

1

2

1

3

4

S 2004 CS325 12

Real and virtual memoryReal and virtual memorylogical

(virtual)real

(physial)

mapping



S 2004 CS325 13

Real and virtual memoryReal and virtual memory

logical (virtual) real (physial)

The ideal situation: each process (executing program) has its own address space ranging from 0 to a max_size. No access from/to other address spaces is allowed.

The real situation: each memory system is composed of a hierarchy of storage components (cache, fast and big memory…). The total storage is divided into segments, pages and access/ transfer pieces – proper access and protection is a serious problem.

Special hardware support (paging, base and limimt registers, address mapping hardware (MMU) alleviate the task of the operating system.

S 2004 CS325 14

Virtual,Virtual, logicallogical und und physicalphysical devicesdevices

virtual device

control data

log. device 1 log. device 2

phys. device 1

phys. device 2

Driver_1 Driver_2



S 2004 CS325 15

interfacesinterfaces andand VirtualVirtual machinesmachines

virtual machine = logical machine + manager

logical machine = physical maschine +driver

Operating Systemkernel

S 2004 CS325 16

Virtual MachinesVirtual Machines

Hardware

Virtual Machine

Kernel_1 Kernel_2 Kernel_3

Processes Processes Processes



S 2004 CS325 17

Example Example VirtuVirtuaal Machinel Machine

Hardware

Virtual Machine (VM/370)

OS_1 OS _2 OS _3

Processes Processes Processes

S 2004 CS325 18

System ConfigurationSystem Configuration

CPUmemory

controller

terminal

controllercontroller

secondary storage

controller

controller

printertape/C

D

netw.interf.



S 2004 CS325 19

structural organization structural organization

user_1 user_2 user_napplication programs

System-Libraries (functions)

OS-kernel

Hardware Plattform

file-system

user-mode

(protected)

system-mode

(priviledged)

S 2004 CS325 20

structural organizationstructural organization

• Monolithic systems: one big collection of routines, all run in privileged mode;

• Structured systems: higher-level functions run in user mode, lower-level functions are combined into a privileged kernel;

• Micro-kernel systems: only the hardware-drivers and a few critical components (thread management, inter-process communication, synchronization) run in kernel mode – everything else runs in user mode.



S 2004 CS325 21

Operating System KernelOperating System Kernel

SoftwareSoftware strustruccturturee

(Graphical) User Interface(Graphical) User Interface

Applic.-progr. 1Applic.-progr. 1

User 1

utility-programutility-

programSW-tool

SW-tool

Applic.-progr. nApplic.-progr. n

User 2 User n

Operating System FunctionsOperating System Functions

HardwareHardware

SystemCalls

Maschinencode

. . .

VM

POSIX

S 2004 CS325 22

„von Neumann Architecture“„von Neumann Architecture“

Memory contains:

• data and

• programs

instructions(commands)

Control unit ALU

data

control-signals

Data (results)Adress of next instruction

This principle was invented by J. P. Eckert and J. W. Mauchly but published first as an abstract concept by John von Neumann.Similar ideas were developed by Konrad Zuse and Schreyer.



S 2004 CS325 23

FetchFetch--Execute CycleExecute Cycle

REPEATIR := Mp[PC];PC := PC+1IF (FC == JpClass) THEN

PC := OperandELSE

Execute (IR)END_IF;

UNTIL cpu_HALT;

jumps

other operations

S 2004 CS325 24

von Neumann Architecture (SISD)von Neumann Architecture (SISD)

memory Mp contains:

• data and

• programs

instruction

Program Counter PC instruction register IR

Adress of next instruction

ALUdat

FC OperandMod

Adress, direct Operandfunction code

modifier



S 2004 CS325 25

Interrupt MechanismInterrupt Mechanism

ELSE

IF (FC == JpClass) THEN PC := Operand

ELSE Execute (IR);

END_IF

save PC; PC := IRLoc_i

IF (IRQ_i == 1) THEN

IR := Mp[PC]; PC := PC+1

END_IF // Interrupt

S 2004 CS325 26

„basic instruction cycle with interrupts“„basic instruction cycle with interrupts“nxnynz

nnn_i

nxnyni

This transition is triggered by the interrupt

This transition is executed by the interrupthandler (driver) command “RTI”

This location is saved by the interrupthardware or the handler software.



S 2004 CS325 27

Software StructureSoftware Structure

(Graphical) User Interface – „shell“(Graphical) User Interface – „shell“

application 1application 1

User 1

Utility iUtility i Tool kTool k application napplication n

User 2 User n

Operating System kernel

Hardware

System Calls (SVC)

. . .

Operating SystemFunctions and Services

S 2004 CS325 28

OS Functions OS Functions

• Process management

• Memory management

• File management5

• Input/Output

• Networking

• Utility services



S 2004 CS325 29

Simple batch system Simple batch system –– memory allocationmemory allocation

Operating system

- data

User program- code

free space

0

FF….FF

S 2004 CS325 30

Bootstrap LoaderBootstrap Loadertask: load a small initial program into memory and start it.

This process is also called „deadstart“, „coldstart“, „bootstrap“; it must be supported by a hardware “initial load” function.

Press_Load:

FOR i := 0 TO 79 DO

Read(M[i]);

END_FOR;

GOTO (M[0]);



S 2004 CS325 31

BootstrapBootstrap

Entry_Address = start of execution ( PC := E_A; go! )

LA1 Absolute Code (Program/Data)n1

10 79



E_A 0

.. ........

S 2004 CS325 32

BootstrapBootstrapIn a second/third phase the minimal program can read and sub- sequently start a bigger program - e.g. a more powerfulloader or the kernel of an executive system (Exec, Monitor program, OS)

LOOP:FOR i := 0 TO 79 DO Read(M[r+i]) END_FOR;LA := M[r]; n := M[r+1];IF n==0 THEN GOTO LA;FOR i := 0 TO n-1 DO

M[LA+i] := M[r+2+i] END_FOR;END_LOOP;

LA

Load address

Absolute Code (Program/Data)n

10 79



S 2004 CS325 33

Bootstrap Loader Bootstrap Loader

3 loading stages

Operating system Main memory

S 2004 CS325 34

Bootstrap Loader IIBootstrap Loader IIInitially a HW program (ROM) reads the firstsector of the boot disk with the “Partition Table”; then it reads the bootblock of the active partition.

All other steps are identical to the simple boot process.

1 2

3



S 2004 CS325 35

Early ProgrammingEarly Programming

• Use of the „bare machine“

• Certain instruction sequences which appear frequently are arranged into subroutines

• Subroutines which are commonly used are organized into a library

for application programming a symbolic notation is introduced -> Assembler FC „64“ = „jmp“

• Address managment is alleviated by introducing symbolic names and automatic relocation at translation and loading time

S 2004 CS325 36

Early ProgrammingEarly Programming• Binding (linkage edit) und Loading are delegated to special

programs. (linkage editor, loader)

• Execution is supervised and controlled by a „Monitor“ program (Exec).

• Additional service programs (utilities) are provided: editor, compiler, SortMerge programs

• Control cards and a „Job Control Language“ (JCL) permit user control of „job“ execution

• all systems and utility programs comprise the operating software; the machine-oriented programs lower layers form the operating system proper.



S 2004 CS325 37

user mode

kernel mode

protected

unprotected = privileged

bare hardware

S 2004 CS325 38

Multiprogramming systeme Multiprogramming systeme --memory allocationmemory allocation

operating system

user job_1

User job_2

user job_n

Jan 26



S 2004 CS325 39

CPU and I/O ActivitiesCPU and I/O Activities

Zeit t

Akt

ivitä

t

CPU

I/O

Inte

rrup

t

Inte

rrup

t

S 2004 CS325 40

I/O OverlapI/O Overlap ((Multiprogramming Multiprogramming //MultitaskingMultitasking))

Zeit t

Akt

ivitä

t

CPU

I/O

Inte

rrup

t

Inte

rrup

t

CPU

I/O

Process 1

Process 2

Process 1

Process 1



S 2004 CS325 41

Runtime Organization Runtime Organization -- Service InvocationService Invocation

• Subroutine/Coroutine– Single thread of execution

• Message Passing– Multiple threads

– Logical / virtual

– Physical / real

S 2004 CS325 42

Memory Memory ProtectionProtection

Operating system

job_1

job_n

Basisregister

Limitregister

job_2

Kernel ModeUser Mode

privilegierte Instruktionen

<

>=



S 2004 CS325 43

Protection Protection -- Kernel/User ModeKernel/User Mode

operating system

job_1

job_n

Baseregister

Limitregisterjob_2

Kernel ModeUser Mode

privilegierte Instruktionen

<

>=

PrivilegedInstructions

S 2004 CS325 44

Types of Operating SystemsTypes of Operating Systems

• simple Batch Systems • Timesharing Systems • Workstation / PC Systems• Multiprocessor-/Parallel-systems• Real Time Systems• Process Control Systems• Embedded Systems• Signal processing systems• Distributed Systems• Networked Systems



S 2004 CS325 45

Monolithic SystemMonolithic System

User programs

Operating System

P_1 P_n

HW System

Proc-Call;SVC;

Send/Receive;

Call;Branch;Return;

Interrupt

S 2004 CS325 46

ProcessProcess--Oriented SystemOriented SystemUser

process

Operating System Kernel

u_i s_j

HW System

KernelCall Return;

Interrupt

System process

communication



S 2004 CS325 47

ObjectObject--Oriented SystemOriented SystemUser

object

Operating System Kernel

o_i o_j

HW System

KernelCall Return;

Interrupt

System object

capability

S 2004 CS325 48

Future?Future?

• “current efforts to secure the PC´s traditionally open architecture will either lead – to an unwieldy system that tries to employ impenetrable

membranes, encrypted buses and tamper resistant memory, or

– To an inferior solution that fails to thwart dishonest users andlimits backup and interoperability “

• “investing in proven architectural improvements such as guarded pointers and data tags (capabilities) is a more cost effective and long overdue alternative”



S 2004 CS325 49

Yet another quote…Yet another quote…“The world of software production has dramatically changed during the last decades from pure assembler programming to procedural programming to object-oriented programming. Each step raised the level of abstraction and increased programmer productivity. Operating systems, on the other hand, remained largely unaffected by this process.

… there is a growing divergence between application programming and operating system programming. To close this semantic gap between the applications and the OS interface a large market of middleware systems has emerged over the last years.

While these systems hide the ancient nature of operating systems, they introduce many layers of indirection with several performance problems.

While previous object-oriented operating systems demonstrated that it is possible and beneficial to use object-orientation, they also made it apparent that it is a problem when implementation technology (object orientation) and protection mechanism (address spaces) mismatch.”

S 2004 CS325 50

Not a pretty picture …Not a pretty picture …

Application program

Application program

Middleware

API

Operating System

Hardware

KI



S 2004 CS325 51

CPU und I/O activity CPU und I/O activity –– (a) instruction waits(a) instruction waits

time t

CPU

I/O

I/O instruction

I/O deviceidle idle

I/O routine

I/O routine I/O

instruction

S 2004 CS325 52

II//OO aand CPU nd CPU OvOverlapperlappiingng

inaktiv

aktiv

inaktiv

aktiv

InterruptCommand

111CPU

I/O idle

idle

READY

READY



S 2004 CS325 53

CPU und I/O activity CPU und I/O activity –– (b) parallel I/O with (b) parallel I/O with pollingpolling

time t

CPU

device I/O deviceidle idle

I/O routine

I/O routine

test

rest

art

busy

test

test

test

rest

art

test

test

S 2004 CS325 54

CPU und I/O activity CPU und I/O activity –– (c) device interrupts (c) device interrupts CPUCPU

time t

CPU

device

I/O deviceidle idle

I/O routine

I/O routine

inte

rrup

t

rest

art

busy

inte

rrup

tre

star

t

inte

rrup

t



S 2004 CS325 55

The basic structure of protection rings (Multics)

S 2004 CS325 56

XINU

Is Not Unix !

Douglas Comer: Operating System Design – the XINU Approach (LSI-11, Pentium)



S 2004 CS325 57

Design PrinciplesDesign Principles

• Functionality vs. form• components – composition - aggregation • Concentrate on basic design elements and functions

(the logical level, not implementation aspects ??)• Follow the KISS principle: (keep it simple, stupid!)• Aside: implementation principles:

– Use HL implementation languages!

– Compilers need to efficiently exploit the HW (JIT)

– Exploit efficient basic methods, e.g.* Fast context switching (address space)* Highly efficient IPC* Efficient process/thread switching and RPC

S 2004 CS325 58

Layered StructureLayered Structure

Hardware

System services

Compiler ProgrammEditor

User_1 User_2 User_n

Hard-ware

System kernel



S 2004 CS325 59

Layered SystemsLayered Systems

• Layer – a collection of functions which are closely coupled and at the same hierarchical level

• hierarcal level - corresponds to a certain level of abstraction

• abstraction – extraction of the essential (logical) characteristic features of a real (physical) machineand definition of an abstract (logical) machine

• The services are made available by “system calls” (SVCs) in form of standardized functions at APIs[API - application program interface, SAP - service access point ]

S 2004 CS325 60

“virtualization”“virtualization”

Processing –step

Layer 3

Layer 1

Layer 2

Processing -step

Processing -step

time

Java

Java-VM

e.g. Pentium



S 2004 CS325 61

HAL and virtuHAL and virtualal mmachineachiness• A Hardware Abstraction Layer (HAL) is an attempt to map the

physical characteristics of hardware onto a more abstract and general logical machine.

• A virtual machine offers to the user a certain interface which generates the illusion of a “real” machine.

• The different layers of an operating system can be seen as virtual machines of increasingly higher abstraction.

• Different virtual machines can coexist in one real system at thesame level and in multiprogramming mode.

• The „Java VM“ supports specifically the concepts and structureof the high-level programming system Java; this (should) guarantee the portability of applications (and late binding/dynamic loading as well as JIT compiling).

S 2004 CS325 62

GoalsGoals

• Design goals – “elegant and clean”• Implementation goals – “efficient and compact”

• 2 competing views:– Top-down – goal oriented (deductive)

– Bottom-up – tool oriented (inductive)

• Common goal: both approaches concentrate on the kernel– Micro – kernel

– Exo – kernel

• *** the kernel design and implementation is the *** real problem



S 2004 CS325 63

Cont.Cont.

• The common elements are:– Improved protection mechanisms to support “trusted

systems”

– Highly efficient set of basic elements (functions, primitives, objects)

– Extensibility I.e. the capability to dynamically load additional OS components such as e.g. drivers in a “safe and secure” mode

S 2004 CS325 64

MachMach

kernelmode

usermode

HardwareHardware

Micro-kernel: Scheduler, Interprocess Communic. Basic I/O

Memory

Management

File

System

Terminal

I/O

Interface tosystem calls

and functions

User 1 User 2 . . .



S 2004 CS325 65

Windows NT StrukturWindows NT Struktur

HardwareHardware

(Mikro) Kernel

Hardware Abstraction Layer

ObjectManager

ProcessManager

MemoryManager

SecurityManager

Local Proc.Calls

Executive - Systemdienste

kernelmode

usermode

I/OManager

Win32Subsyst.

security Subsyst.

Win16 VDM

OS/2applic.

POSIXSubsyst.

MSDOSVDM

OS/2Subsyst.

Win16applic.

POSIXapplic.

MSDOSapplic.

WIN32applic.

Logon proc.

operating systems principles design and implementation ...cs325/osp_01.pdf · os_1 os _2 os _3...

Documents