Post on 03-Jan-2016
description
OPERATING SYSTEMS PRINCIPLES
Instructor: Xiangluo Wang
E-Mail: wx_25@yahoo.com.cn
Office: Yifu A404
Office Hours: Thursdays@ 16:00-18:00,or by appointment
Preface• GOALS
Devoting to traditional topicsExtending & Integrating them with basic ideas in
distributed computingEmphasizing language application
• CONTENTSProcess Management and CoordinationMemory ManagementFile and I/O ManagementProtection and Security
Preface
• EXERCISESAnalytical contentsConstructive contentsDiscussion or speculative analysis
• APPROACH & PHILOSOPHY In-depth coverage of standard topics Integrating centralized and distributed OS issues in eac
h chapter Introducing various cases of existing os throughout the
course
CHAPTER 1
THE ROLE OF OPERATING SYSTEMS
ORGANIZATION OF OPERATING SYSTEMS
OPERATING SYSTEM EVOLUTION AND
CONCEPTS
INDEX:
THE ROLE OF OPERATING SYSTEMS
• Bridging the Hardware/Application Gap
• As Extended Machines
• As Virtual Machines
• As Resource Managers
Fetch the instruction pointed to by the program counter
Increment the program counter
Decode the current instruction
Fetch any operands referenced by the instruction
Execute the instruction
FIGURE 1-1 Basic hardware cycle
Main
memory
CPU Communication
devices
Secondary
storage
User
Network
FIGURE 1-2 Main components of a computer system
Main
memory
CPU
CPU
Communication
devices
Secondary
storage
FIGURE 1-3 Shared-memory multiprocessor
Main
memoryCPU
CPU
Communication
devices
Secondary
storage
Main
memory
FIGURE1-4 Distributed-memory multiprocessor
Main
memoryCPU
CPU
Communication
devices
Secondary
storage
Main
memory
Secondary
storage
Communication
devices
Netw
ork
FIGURE 1-5 Multicomputer
LARGE DIVIDE BETWEEN HARDWARE AND APPLICATION:
Machine instructions
Read or write a value------High-level data structures
Perform arithmetic/logical operation-----Complex control flows
Main memory
A linear sequence of simple cells------programs, modules, and data structures
Secondary storage
Tracks, blocks------file
Hardware interface and I/O device
Registers-------messages
Three Views of operating systems
• Abstraction:
Being applied to handle complexity• Virtualization:
resource sharing• Resource management:
The problem of efficiency
KEY CONCEPTS:
OS as Extended Machines
• Abstraction:package sequences of lower-level instructions into functions that can be invoked as single higher-level operations
• Making use of abstraction at many levels
OS as Virtual Machines
CPU1 CPU2
CPU
Virtual memory1
Virtual memory2
Main memory
Printer1 Printer2
Printer
Application1
Time sharing
Memory management
Spooling
OS
Hardw
are
Principles of virtualization
Task’s VM space in Linux
User
kernel
CS
DS
BSS
HEAP
STACK
HOLE
3GB
1GB
OS as Resource Managers
• Difference between devices’ performance
• Parallelism opportunities
• Scheduling policies
ORGANIZATION OF OS
• Structural Organization (functional)
• Internal structure (static)Hardware InterfaceProgramming InterfaceUser Interface
• Runtime Organization
Structural Organization
Applications
(system and user)
OS kernel
System libraries
Hardware
User
Library calls
Kernel calls
Machine instructions
Hardware Interface
• Interrupts, Singularities, and TrapsExternal interrupts (Hardware)Internal interrupts
Soft interruptsSelf trapsSingularities
• Modes of Instruction Execution
X86:Ring 0—Ring 3
Example
• Clock interrupt in LinuxSeveral hardware clock interrupts contribute one “tick”;
One “tick” causes the change of execution mode .
• Task schedule& switchOccurring in Ring 0
• User mode& kernel mode
Linux: Ring0& Ring3;
OS2: Ring0---Ring3
The Programming Interface
• The difference between kernel and library functions
• Sys-calls provided by OSs
Application issues call
To lib_func(params)
Body of
Lib_func()
Push params on stack
Branch to lib_func() bodyPerform service
Return from functionPop stack pointer
Nonprivileged library service
Application issues call
To kern_func(params)
Body of
kern_func()
Push params on stack
Branch to kern_func() body Set up regs for SVC
SVC
Pop stack pointer
Nonprivileged library service
Return from function
Kernel code
Perform service
Set nonprivileged mode
Return from SVC
Sys-calls
• Process management
--create/destroy, suspend/activate process
--send signal or message to process
--wait for event or signal• Memory management
--allocate/deallocate region of memory
--increase/decrease size of allocated region
Sys-calls
• File management
--create/destroy, open/close, move, rename file
--append data to file or concatenate files
--display content of file or directory
--display/change file attributes
Sys-calls
• Input/Output--read/write character or block of data from a file o
r device
--control/check status of a device
• Miscellaneous services--get current date and time
--schedule an alarm to occur
--generate various system diagnostics
The User Interface
The top-level user interface remains available at all times so that users can launch, use, monitor, and manage applications and files– Text-based interface (shell)– Graphics-based interface (GUI)
The Shell• Execute and manage programs
ar: create, edit,modify source files
as: compiler
ld: GNU linker
gdb: GNU DeBug
• Manipulate filesmkdir, rm, mv, rmdir, cat
• Obtain system informationwho, pwd,du, ls
The Shell
• Shell scriptslocal variables
iterative statements
conditionals
arithmetic and logical operators
Wildcards
connectors
Runtime Organization
User process
Library or kernel call
Service routinereturn
Service as a subroutine
Process’ address space
User process (client)
Return results
Send request
Service routine
Process1’s address space
Process2’s address space
System process (server)
Service as a process
Benefits of the C/S approach
• Being suitable for a distributed system
• Being convenient for different types of services
• Having a greater degree of fault tolerance
• Enforcing a strict segregation of functionalities
OS EVOLUTION&CONCEPTS
• Early systems
• Batch OSs
• Multiprogramming Systems
• Interactive OSs
• PC and Workstation OSs
• Real-Time OSs
• Distributed OSs
Early Systems
• Users interact with computations
• One at a time
• At the lowest machine level
• A standard operating procedureLoaderassemblersource programloaderexe machine code
• Initial startup (bootstrapping)
Batch OSs
• Automating the standard load/translate/load/execute sequence
• Job-to-job transitions automatically
• Submitting multiple jobs at the same time
• I/O processor (I/O channel)
Multiprogramming Systems
• A simultaneous manner
• Virtual parallelism (concurrence)
• Protection
• Process synchronization and communication
• Dynamic memory management
Job A
CPU
IO
Job B
Sequential execution
Job A
IOA
CPUA
CPUB
IOB
Job B
multiprogramming
CPU and I/O overlap
Interactive OSs
• The ability to simultaneously share a machine’s resources
• Acceptable response time to each user
• Serve processes cyclically by assigning a small portion or quantum of CPU time
PC and Workstation OSs
• The development of GUIs
• Manually switching
• Implicit multiprogramming (multitasking)Being transparent to the interactive user but not to
applications
• Preemptive multiprogrammingBeing transparent not only to users but to applications
Real-Time OSs
• Timing constraints (deterministic deadlines)
• Concurrency (asynchronous, simultaneous)
• Strict fault tolerance and reliability requirements
• Difficult to test and certify
Distributed OSs
• Loosely coupledCommunicates at a lower level (e.g., over a WAN)
• Tightly coupledhigher-level communication on top of message passing (RP
C)
• Clocks must be synchronized, accurate, and monotomic increasing
EXERCISES
• Give examples of semantic gaps that must be bridged by software,including OSs at the following levels: CPU (instruction) level, main memory level, secondary storage level, I/O device level.
• What do traps and interrupts have in common? How are they different? Give an example of each.
EXERCISES
• What do multiprogramming and time-sharing have in common? How are they different? Is multiprogramming possible without interrupts? Is time-sharing possible without interrupts?