操作系统英文教学课件Chapter-4-Threads

Chapter4:ThreadsChapter4:Threads

Overview

MultithreadingModels

ThreadingIssues

PthreadsOperatingSystemConcepts–7thedition,Jan23,20054.2Silberschatz,GalvinandGagne©2005Threadconceptoverview

AthreadisabasicunitofCPUutilization;

itcomprisesathreadID,aprogramcounter,aregisterset，andastack.

Itshareswithotherthreadsbelongingtothesameprocess：thecodesection,thedatasection,andotherOSresources，suchasopenfiles,signals,etc

Atraditionalprocesshasasinglethreadofcontrol:

heavyweightprocess.OperatingSystemConcepts–7thedition,Jan23,20054.3Silberschatz,GalvinandGagne©2005SingleandMultithreadedProcessesOperatingSystemConcepts–7thedition,Jan23,20054.4Silberschatz,GalvinandGagne©2005Motivation

OnmoderndesktopPC,manyAPPsaremultithreaded.

aseperateprocesswithseveralthreads

Example1:Awebbrowser

onefordisplayingimagesortext;

anotherforretrievingdatafromnetwork

Example2:Awordprocessor

onefordisplayinggraphics;

anotherforrespondingtokeystrokesfromtheuser;

andathirdforperformingspelling&grammercheckinginthebackgroundOperatingSystemConcepts–7thedition,Jan23,20054.5Silberschatz,GalvinandGagne©2005Motivation

Incertainsituations,asingleapplicationmayberequiredtoperformseveralsimilartasks.Example:awebserver

Allowaservertoserviceseveralconcurrentrequests.Example:anRPCserver

TheOSitselfneedstoperformsomespecifictasksinkernel,suchasmanagingdevicesorinterrupthandling.

PARTICULAR,manyOSsystemsarenowmultithreaded.

Example:Solaris,LinuxOperatingSystemConcepts–7thedition,Jan23,20054.6Silberschatz,GalvinandGagne©2005Benefits

Responsiveness

Example:aninteractiveapplicationsuchaswebbrowser.whileonethreadloadinganimage,anotherthreadallowinguserinteraction

ResourceSharing

memory,andotherresources

Economy(e.g.savememory)

Solaris:creatingaprocessisabout30timesslowerthencreatingathread;contextswitchingisabout5timesslower

UtilizationofMPArchitectures

parallelismandconcurrencyOperatingSystemConcepts–7thedition,Jan23,20054.7Silberschatz,GalvinandGagne©2005TwoMethods

Twomethodstosupportthreads

UserthreadsVS.Kernelthreads

UserThreads

Threadmanagementdonebyuser-levelthreadslibrarywithoutkernelsupport

Kernelthreads

SupportedbytheKernel，usuallymaybeslowerthenuserthreadExamples

WindowsXP/2000

Solaris

Linux

Tru64UNIX

MacOSXOperatingSystemConcepts–7thedition,Jan23,20054.8Silberschatz,GalvinandGagne©2005MultithreadingModels

Therelationshipbetweenuserthreadsandkernelthreads

Many-to-One

One-to-One

Many-to-ManyOperatingSystemConcepts–7thedition,Jan23,20054.9Silberschatz,GalvinandGagne©2005Many-to-One

Manyuser-levelthreadsmappedtosinglekernelthread

Examples:

SolarisGreenThreads

GNUPortableThreadsOperatingSystemConcepts–7thedition,Jan23,20054.10Silberschatz,GalvinandGagne©2005Many-to-OneModelOperatingSystemConcepts–7thedition,Jan23,20054.11Silberschatz,GalvinandGagne©2005One-to-One

Eachuser-levelthreadmapstokernelthread

Examples

WindowsNT/XP/2000

Linux

Solaris9andlaterOperatingSystemConcepts–7thedition,Jan23,20054.12Silberschatz,GalvinandGagne©2005One-to-oneModelOperatingSystemConcepts–7thedition,Jan23,20054.13Silberschatz,GalvinandGagne©2005Many-to-ManyModel

Allowsmanyuserlevelthreadstobemappedtomanykernelthreads

Allowstheoperatingsystemtocreateasufficientnumberofkernelthreads

Solarispriortoversion9

WindowsNT/2000withtheThreadFiberpackageOperatingSystemConcepts–7thedition,Jan23,20054.14Silberschatz,GalvinandGagne©2005Many-to-ManyModelOperatingSystemConcepts–7thedition,Jan23,20054.15Silberschatz,GalvinandGagne©2005Two-levelModel

SimilartoM:M,exceptthatitallowsauserthreadtobeboundtokernelthread

Examples

IRIX

HP-UX

Tru64UNIX

Solaris8andearlierOperatingSystemConcepts–7thedition,Jan23,20054.16Silberschatz,GalvinandGagne©2005Two-levelModelOperatingSystemConcepts–7thedition,Jan23,20054.17Silberschatz,GalvinandGagne©2005ThreadLibraries

AthreadlibraryprovidesanAPIforcreatingandmanagingthreads.Twoprimaryways

1.toprovidealibraryentirelyinuserspacewithnokernelsupport2.toimplementakernel