IB HL - Resource Management

8/9/2019 IB HL - Resource Management

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Resource Management

6.1.1. Identify the resources that need to be managed within a computer system

Resources include:

• primary memory

• secondary storage

• processor speed

• bandwidth, screen

resolution

• disk storage

• sound processor

• graphics processor

• cache

• network connectivity

What is a resource?

Here a resource is something that

the CPU (or the CPU itself of a computer has directly or indirectly connected to it that it can use!utili"e#

$ resource, or system resource, is any physical or virtual component of limited availability within a computer system#

%very device connected to a computer system is a resource# %very internal system component is a resource# &irtual

system resources include files, network connectionsand memory areas#

Which resources does a computer need to operate?

$ computer is an electronic device that runs a stored program using a processor (CPU# 'or a CPU to operate it needs a

program that is stored first in a permanent storage device

he minimum of resources a computer needs to function are:

CPU

to process the stored instructions

the CPU has internal resources

o Registers to hold intermediate results of processing actions

o Control Unit to se)uence and coordinate actions in the CPU

o $*U to do the actual arithmetic and logic involved in each program instruction


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RM

• to store a program which will be e+ecuted when the machine is first switched on

R!M

• to allow the CPU to have an available memory storage area that it can use for the program that it is running

"he more things you need your computer to do the more resources it needs to ha#e$

Primary Memory

• allows the CPU a place to hold data while it is processing and remember programs that are currently open

%econdary %torage

• to hold programs including the operating system

• to store files

Processor %peed

• the speed at which the processer operates must be managed by the operating system and depends on the

running of multiple programs via multitasking

&andwidth' %creen Reso(ution

• the passing of data to the monitor!screen must be managed

)is* %torage

• reading and writing to the disk must be managed along with keeping track of where all the files are on the disk

(registries

%ound Processor

• if you want your system to be able to deliver sound to the user then you must manage the processing of digital

audio data and passing it to the analog speakers

+raphics Processor

• to allow the computer to create a visual display the computer must create digital signals that control the pi+els

on a screen# this involves managing the different stages involved

Cache

• a computer can run faster if it has an intermediate type of memory inbetween the ram and the processor that

predicts which data might be needed by the CPU ne+t and operates at a higher speed than R$-

,etwor* Connecti#ity

• if a computer is to be connected to other computers over a network the processing of messages!data between

the computers must be managed

-ou get the idea..

$ll the parts are resources (including the different bits of software involved that manage each area and the more that

you want the computer to be able to do, the more parts (resources you need to get the .ob done# /e can take this ideaand apply it to all the different types of computer we can think# hey all have a range of resources and each resource is

controlled directly or indirectly by the CPU (the Central Processing Unit#

• 0mart Phones

• P1$s

• 2etbooks

• 2otebooks

• 0ervers

• -ain 'rame Computers, etc#


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• outputs simple messages for users if error occur

!dditiona( Information$

• 4i(e %ystems 3 "ypes$

o 'ile $llocation able ('$

table tracking where the data is stored

o 2ew echnology 'ile 0ystem (2'0

introduced by -icrosoft

advantages:

higher reliability errors repaired without message

transaction logs errors tracked

• ypes of 9perating 0ystems:

# 0ingle User -ultiask

e#g# PC

?# -ultiUser

e#g# -ainframe

= -odes of 9peration:

o real time processing

)uick processing of input to generate output

o multiprogramming

seems like multiple programs are running at once programs run according to priority

o interactive processing

continues e+change of information between user computer

o multitasking

tasks run concurrently resources split


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o multiacces or multiuser

same system used via *$2

CPU manages one user after another the more users, the slower

6.1.5 ut(ine % resource management techniues$ schedu(ing' po(icies' mu(titas*ing' #irtua( memory' paging'

interrupt' and po((ing.

Interrupt

/hen an interrupt is received, the computer;s hardware automatically suspends whatever program is currently running,

saves its status, and runs computer code previously associated with the interrupt@ this is analogous to placing a

bookmark in a book in response to a phone call# 7n modern operating systems, interrupts are handled by the operating

system;s kernel#7nterrupts may come from either the computer;s hardware or from the running program#

/hen a hardware device triggers an interrupt, the operating system;s kernel decides how to deal with this event,generally by running some processing code# he amount of code being run depends on the priority of the interrupt (for

e+ample: a person usually responds to a smoke detector alarm before answering the phone# he processing of

hardware interrupts is a task that is usually delegated to software called de#ice dri#er , which may be either part of the

operating system;s kernel, part of another program, or both# 1evice drivers may then relay information to a running

program by various means#

$ program may also trigger an interrupt to the operating system# 7f a program wishes to access hardware for e+ample, it

may interrupt the operating system;s kernel, which causes control to be passed back to the kernel# he kernel will then

process the re)uest# 7f a program wishes additional resources (or wishes to shed resources such as memory, it will

trigger an interrupt to get the kernel;s attention#

here are two types of interrupts:

Hardware interrupts are used by devices to communicate that they re)uire attention from the operating system# 'or

e+ample, pressing a key on the keyboard or moving the mouse triggers hardware interrupts that cause the processor to

read the keystroke or mouse position# Hardware interrupts are asynchronous and can occur in the middle of instruction

e+ecution, re)uiring additional care in programming# he act of initiating a hardware interrupt is referred to as

an interrupt re)uest (7RA#

$ software interrupt is caused either by an e+ceptional condition in the processor itself, or a special instruction in

the instruction set which causes an interrupt when it is e+ecuted#

'or e+ample, if the processor;s arithmetic logic unit is commanded to divide a number by "ero, this impossibledemand will cause a divideby"ero e+ception, perhaps causing the computer to abandon the calculation or display an

error message# 0oftware interrupt instructions function similarly to subroutine calls and are used for a variety of

purposes, such as to re)uest services from lowlevel system software such as device drivers#

Mu(titas*ing

-ultitasking is a method where multiple tasks (also known as processes are performed during the same period oftime 3 they are e+ecuted concurrently (in overlapping time periods, new tasks starting before others have endedinstead of se)uentially (one completing before the ne+t starts# he tasks share common processing resources, such as

a CPU and main memory#

9perating systems may adopt one of many different scheduling strategies, which generally fall into the following

categories:

https://en.wikipedia.org/wiki/Kernel_(computer_science)https://en.wikipedia.org/wiki/Device_drivershttps://en.wikipedia.org/wiki/Keyboard_(computing)https://en.wikipedia.org/wiki/Keyboard_(computing)https://en.wikipedia.org/wiki/Mouse_(computing)https://en.wikipedia.org/wiki/Asynchronous_communicationhttps://en.wikipedia.org/wiki/Interrupt_requesthttps://en.wikipedia.org/wiki/Interrupt_requesthttps://en.wikipedia.org/wiki/Interrupt_requesthttps://en.wikipedia.org/wiki/Instruction_(computer_science)https://en.wikipedia.org/wiki/Instruction_sethttps://en.wikipedia.org/wiki/Arithmetic_logic_unithttps://en.wikipedia.org/wiki/Subroutine_callhttps://en.wikipedia.org/wiki/System_softwarehttps://en.wikipedia.org/wiki/Device_driverhttp://en.wikipedia.org/wiki/Task_(computers)http://en.wikipedia.org/wiki/Computer_processhttp://en.wikipedia.org/wiki/Concurrent_computinghttp://en.wikipedia.org/wiki/Central_processing_unithttps://en.wikipedia.org/wiki/Device_drivershttps://en.wikipedia.org/wiki/Keyboard_(computing)https://en.wikipedia.org/wiki/Mouse_(computing)https://en.wikipedia.org/wiki/Asynchronous_communicationhttps://en.wikipedia.org/wiki/Interrupt_requesthttps://en.wikipedia.org/wiki/Instruction_(computer_science)https://en.wikipedia.org/wiki/Instruction_sethttps://en.wikipedia.org/wiki/Arithmetic_logic_unithttps://en.wikipedia.org/wiki/Subroutine_callhttps://en.wikipedia.org/wiki/System_softwarehttps://en.wikipedia.org/wiki/Device_driverhttp://en.wikipedia.org/wiki/Task_(computers)http://en.wikipedia.org/wiki/Computer_processhttp://en.wikipedia.org/wiki/Concurrent_computinghttp://en.wikipedia.org/wiki/Central_processing_unithttps://en.wikipedia.org/wiki/Kernel_(computer_science)


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• 7n mu(tiprogramming systems, the running task keeps running until it performs an operation that re)uires

waiting for an e+ternal event (e#g# reading from a tape or until the computer;s scheduler forcibly swaps therunning task out of the CPU# -ultiprogramming systems are designed to ma+imi"e CPU usage#

•

7n time3sharing systems, the running task is re)uired to relin)uish the CPU, either voluntarily or by an e+ternalevent such as a hardware interrupt# ime sharing systems are designed to allow several programs to e+ecuteapparently simultaneously#

• 7n rea(3time systems, some waiting tasks are guaranteed to be given the CPU when an e+ternal event occurs#

Real time systems are designed to control mechanical devices such as industrial robots, which re)uire timelyprocessing#

Po((ing

o make a system work, the 90 will need to check regularly if its devices have become ready# his is called po((ing#

he 90 runs at regular intervals (say, once per millisecond to check each device to see if it is ready# 7f ready, then the

90 further deals with the device#

• 'or a ready keyboard, the character typed is placed into a )ueue#

• 'or a ready display, the )ueue is checked# 7f not empty, then the ne+t character in the )ueue is sent to the

device#

Memory management$ he process of keeping track of what programs are in memory and where in memory theyreside

Process$ $ program in e+ecution

Process management$ he act of carefully tracking the progress of a process and all of its intermediate states

%chedu(ing

9ne of the primary functions of an operating system is to distribute the resources under its control among the users of

the system in such a way as to achieve installation standards of performance (including service#0cheduling determines which process in memory is e+ecutedby the CPU at any given point# 7t is method by which

threads, processes or data flows are given access to system resources (e#g# processor time, communications

bandwidth# his is usually done to load balance and share system resources effectively

%chedu(ing Po(icies7 !(gorithm

http://en.wikipedia.org/wiki/Multiprogramminghttp://en.wikipedia.org/wiki/Multiprogramminghttp://en.wikipedia.org/wiki/Time-sharinghttp://en.wikipedia.org/wiki/Time-sharinghttp://en.wikipedia.org/wiki/Hardware_interrupthttp://en.wikipedia.org/wiki/Hardware_interrupthttp://en.wikipedia.org/wiki/Real-time_computinghttp://en.wikipedia.org/wiki/Real-time_computinghttp://en.wikipedia.org/wiki/Real-time_computinghttp://en.wikipedia.org/wiki/Thread_(computer_science)http://en.wikipedia.org/wiki/Process_(computing)http://en.wikipedia.org/wiki/Process_(computing)http://en.wikipedia.org/wiki/Flow_(computer_networking)http://en.wikipedia.org/wiki/Flow_(computer_networking)http://en.wikipedia.org/wiki/Flow_(computer_networking)http://en.wikipedia.org/wiki/Load_balancing_(computing)http://en.wikipedia.org/wiki/Multiprogramminghttp://en.wikipedia.org/wiki/Time-sharinghttp://en.wikipedia.org/wiki/Hardware_interrupthttp://en.wikipedia.org/wiki/Real-time_computinghttp://en.wikipedia.org/wiki/Thread_(computer_science)http://en.wikipedia.org/wiki/Process_(computing)http://en.wikipedia.org/wiki/Flow_(computer_networking)http://en.wikipedia.org/wiki/Load_balancing_(computing)


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8irtua( Memory

$n imaginary memory area supported by some operating systems (for e+ample, /indows but not 190 in con.unctionwith the hardware# Bou can think of virtual memory as an alternate set of memory addresses#

he purpose of virtual memory is to enlarge the address space, the set of addresses a program can utili"e# 'or

e+ample, virtual memory might contain twice as many addresses as main memory# $ program using all of virtual

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memory, therefore, would not be able to fit in main memory all at once# 2evertheless, the computer could e+ecute such

a program by copyinginto main memory those portions of the program needed at any given point during e+ecution#

o facilitate copying virtual memory into real memory, the operating system divides virtual memory into pages, each of

which contains a fi+ed number of addresses# %ach page is stored on a diskuntil it is needed# /hen the page is needed,

the operating system copies it from disk to main memory, translating the virtual addresses into real addresses#

Paging

7n computer operating systems, paging is one of the memorymanagement schemes by which a computer can store and

retrieve data from secondary storage for use in main memory# 7n the paging memorymanagement scheme, the

operating system retrieves data from secondary storage in samesi"e blocks called pages# he main advantage of

paging over memory segmentation is that it allows the physical address space of a process to be noncontiguous# 5efore

paging came into use, systems had to fit whole programs into storage contiguously, which caused

various storage and fragmentation problems#

Paging is an important part of virtual memory implementation in most contemporary generalpurpose operating systems,

allowing them to use secondary storage for data that do not fit into physical randomaccess memory (R$-#

he main functions of paging are performed when a program tries to access pages that are not currently mapped to

physical memory (R$-# his situation is known as a page fault# he operating system must then take control and

handle the page fault, in a manner invisible to the program# herefore, the operating system must:

• 1etermine the location of the data in secondary storage#

• 9btain an empty page frame in R$- to use as a container for the data#

• *oad the re)uested data into the available page frame#

• Update the page table to refer to the new page frame#

• Return control to the program, transparently retrying the instruction that caused the page fault#

hrashing

/hen paging are used, a problem called 6thrashing6 can occur, in which the computer spends an unsuitably large

amount of time transferring pages to and from a backing store, hence slowing down useful work# he phenomena is

associated with the concept of a working set which is the minimum set of pages that should be in memory in order for

useful progress to be made in a task# hrashing occurs when there is insufficient memory available to store the working

sets of all active programs# $dding real memory is the simplest response, but improving application design, scheduling,

and memory usage can help# $nother solution is to reduce the number of active tasks on the system# his reduces

demand on real memory by swapping out the entire working set of one or more processes#

%poo(ing

7n computing, 0P99* is an acronym for simultaneous peripheral operations online# 7t is a type of buffering# he most

common spooling application is print spooling, which places a task (or ;print .ob; into a )ueue for e+tended or later

processing#

he most common spooling application is print spooling: documents formatted for printing are usually stored into an

area on a disk and retrieved and printed by a printer at its own rate# Printers typically can print only a single document at

a time and re)uire seconds to minutes to do so# /ith spooling, multiple processes can write documents to a print )ueue

without waiting# $s soon as a process has written its document to the spool device, the process can perform other tasks,

while a separate printing process operates the printer#

'or e+ample, when a city prepares payroll checks, the actual computation may take a matter of minutes or evenseconds, but the printing process might take hours# 7f the program printed directly, computing resources (CPU, memory,

peripherals would be tied up until the program was able to finish# he same is true of personal computers# /ithout

spooling, a word processor would be unable to continue until printing finished# /ithout spooling, most programs would

be relegated to patterns of fast processing and long waits, an inefficient paradigm#

http://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/C/copy.htmlhttp://www.webopedia.com/TERM/C/copy.htmlhttp://www.webopedia.com/TERM/P/page.htmlhttp://www.webopedia.com/TERM/D/disk.htmlhttps://en.wikipedia.org/wiki/Computerhttps://en.wikipedia.org/wiki/Computerhttps://en.wikipedia.org/wiki/Computerhttps://en.wikipedia.org/wiki/Operating_systemhttps://en.wikipedia.org/wiki/Operating_systemhttps://en.wikipedia.org/wiki/Memory_managementhttps://en.wikipedia.org/wiki/Computer_data_storage#Secondary_storagehttps://en.wikipedia.org/wiki/Computer_data_storage#Secondary_storagehttps://en.wikipedia.org/wiki/Computer_data_storage#Primary_storagehttps://en.wikipedia.org/wiki/Computer_data_storage#Primary_storagehttps://en.wikipedia.org/wiki/Computer_data_storage#Primary_storagehttps://en.wikipedia.org/wiki/Block_(data_storage)https://en.wikipedia.org/wiki/Block_(data_storage)https://en.wikipedia.org/wiki/Memory_segmentationhttps://en.wikipedia.org/wiki/Memory_segmentationhttps://en.wikipedia.org/wiki/Memory_segmentationhttps://en.wikipedia.org/wiki/Contiguous#Computer_sciencehttps://en.wikipedia.org/wiki/Contiguouslyhttps://en.wikipedia.org/wiki/Contiguouslyhttps://en.wikipedia.org/wiki/Contiguouslyhttps://en.wikipedia.org/wiki/Computer_data_storagehttps://en.wikipedia.org/wiki/Computer_data_storagehttps://en.wikipedia.org/wiki/Fragmentation_(computer)https://en.wikipedia.org/wiki/Fragmentation_(computer)https://en.wikipedia.org/wiki/Virtual_memoryhttps://en.wikipedia.org/wiki/Virtual_memoryhttps://en.wikipedia.org/wiki/Random-access_memoryhttps://en.wikipedia.org/wiki/Random-access_memoryhttps://en.wikipedia.org/wiki/Page_faulthttps://en.wikipedia.org/wiki/Page_faulthttps://en.wikipedia.org/wiki/Page_faulthttps://en.wikipedia.org/wiki/Page_tablehttps://en.wikipedia.org/wiki/Instruction_(computer_science)https://en.wikipedia.org/wiki/Instruction_(computer_science)http://en.wikipedia.org/wiki/Paginghttp://en.wikipedia.org/wiki/Paginghttp://en.wikipedia.org/wiki/Paginghttp://en.wikipedia.org/wiki/Thrashing_(computer_science)http://en.wikipedia.org/wiki/Working_sethttp://en.wikipedia.org/wiki/Working_sethttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/C/copy.htmlhttp://www.webopedia.com/TERM/P/page.htmlhttp://www.webopedia.com/TERM/D/disk.htmlhttps://en.wikipedia.org/wiki/Computerhttps://en.wikipedia.org/wiki/Operating_systemhttps://en.wikipedia.org/wiki/Memory_managementhttps://en.wikipedia.org/wiki/Computer_data_storage#Secondary_storagehttps://en.wikipedia.org/wiki/Computer_data_storage#Primary_storagehttps://en.wikipedia.org/wiki/Block_(data_storage)https://en.wikipedia.org/wiki/Memory_segmentationhttps://en.wikipedia.org/wiki/Contiguous#Computer_sciencehttps://en.wikipedia.org/wiki/Contiguouslyhttps://en.wikipedia.org/wiki/Computer_data_storagehttps://en.wikipedia.org/wiki/Fragmentation_(computer)https://en.wikipedia.org/wiki/Virtual_memoryhttps://en.wikipedia.org/wiki/Random-access_memoryhttps://en.wikipedia.org/wiki/Page_faulthttps://en.wikipedia.org/wiki/Page_tablehttps://en.wikipedia.org/wiki/Instruction_(computer_science)http://en.wikipedia.org/wiki/Paginghttp://en.wikipedia.org/wiki/Thrashing_(computer_science)http://en.wikipedia.org/wiki/Working_set


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6.1.9 ut(ine how an operating system hides the comp(e:ity of the hardware from users and app(ications.

!bstraction$

90 abstraction layers deal with presenting an abstraction (hides of the details of the different hardware configurations,

thereby ensuring that application do not need to be tailored for each possible device that might be present on thesystem


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/hat resources are managed in a computer system

D Primary memory (R$-

D 0econdary storage (hard drive!disk storage

D Central Processing Unit (CPU

D 4raphical Processing Unit (4PU

D 2etwork bandwidth!connectivity

D 0creen resolutionD 0ound processor

How do resources differ on different systems

D Cost vs# Performance

D 2o need to spend money on e+tra hardware if it is not needed

D %+amples:

D 0creens for mainframes and servers

D Hard drives for cell phones

D 4PU for an ebook

/hat problems could occur from limited resources

D *imited memory à use of secondary storage as memory

D 0econdary storage is slower à time lost

D *imited CPU à programs run slower or system stalls

D *imited 4PU à choppy, undetailed graphics

D *imited network connectivity à constant buffering and delays

9perating 0ystem Roles

D Hardware management

D Communicating with all hardware

D Resource monitoring

D processor time, memory usage, etc#

D Coordinating concurrent processing

D multiple programs (processes running at the same time

D -emory management

D each program has their own space in memory

D EE9perating system hides the comple+ activities above from the userFEE

-ultiprocessing!-ultitasking

D -emory allocation

D *oad program from hard drive into a section of memory (R$-D imeslicing (sharing CPU time across programs

D 4iving a particular program a Gslice of time to run

D Priority

D $ program can be given Gpriority if itIs more important

D e#g# window in focus, streaming services

&irtual -emory

D /hat happens when you run too many programs and all of the memory is used up /hat other storage is

there

D How do we keep some memory free at all times


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&irtual -emory erms

D Paging ! 0wapping

D -oving program data between memory and disk

D /here do you see this stuff

D pagefile#sys in windows

D !swap space in linu+

D /henever you use up all your R$- and your hard drive goes cra"y#D 9ptimi"ations

D /hole programs do not have to fit in memory contiguously (all in one section

D Prevents memory segmentation

D Preemptive paging

1iscussion: /hy are there different operating systems

D -ac 90 8 vs# i90

D Ubuntu *inu+ vs# $ndroid

D $dvantages (Hint: think in terms of design

How does the 90 represent hardware devices

D Hardware comple+ities are hidden from the user by the 90

D Hardware is simplified and represented virtually by the 90

D %+amples

D -ouse pointer

D 'ile tree and drive letters

D 9thers

90 ßà Hardware Communication

D How does the 90 know Gwhen to communicate with hardware

D 7nterrupt vs# Polling

D /hat do you think they mean

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