Operating Systems 202 1 3031 Roie Zivan Office
- Slides: 53
Operating Systems (202 -1 -3031) Roie Zivan ü Office: 16 build. , 261 ü zivan. roie@gmail. com ü Office hours: Sundays, 09: 00 -10: 00 – appointments only Lecturers: Roie Zivan TAs: Vadim Levit, Benny Lutati Course site: site http: //www. cs. bgu. ac. il/~os 163/Main
Assignments and grade structure Assignment Subject Weight Programming 1 + 2 System-calls +Scheduling 15% Programming 3 + 4 Synchronization + Memory Management 15% Final 70% All q Assignments are performed on XV 6 q All Assignment and XV 6 related questions will be answered by the TAs. q Assignments and exams are mandatory q Must pass final exam
Textbooks q A. Tanenbaum: Modern Operating Systems, Prentice-Hall, 3 rd Edition, 2008 q A. Silbetschatz et al. : Operating System Concepts (9 th ed. ), Addison Wesley, 2012 q G. Nutt: Operating Systems (a modern perspective) (3 rd ed. ), Addison Wesley, 2003 q W. Stallings: Operating Systems (6 th ed. ), Prentice-Hall, 2009 Operating Systems, summer 2016 3
Syllabus 1. Introduction - History; Views; Concepts; Structure 2. Process Management - Processes; State + Resources; Threads; Unix implementation of Processes 3. Scheduling – Paradigms; Unix; Modeling 4. Synchronization - Synchronization primitives and their equivalence; Deadlocks 5. Memory Management - Virtual memory; Page replacement algorithms; Segmentation 6. File Systems - Implementation; Directory and space management; Unix file system; Distributed file systems (NFS) 7. Distributed Synchronization (if there's time) Operating Systems, summer 2016 4
Introduction: outline q. What is an operating system? q. Some history q. OS concepts q. OS structure Operating Systems, summer 2016 5
Layered Hardware-Software Machine Model Operating Systems, summer 2016 6
Computer-System Architecture Operating Systems, summer 2016 7
What is an Operating System ? An operating system is: 1. An Extended Machine 2. A Resource manager Operating Systems, summer 2016 8
Operating Systems as extended Machines The problems: q. Bare machine has complex structure o Processors o Many difficult-to-program devices q. Primitive Instruction Set q. Different for Different Machines OS provides: Abstraction! – Simple, easier to use interface (machine-independent) – Hiding of unnecessary details Operating Systems, summer 2016 9
OS abstraction example: read from disk Read file data from disk (simplified) … q q Read linear sector 17, 403 from disk 2 Convert linear sector number to: cylinder, sector, head (may be complicated – outer cylinders have more sectors, bad sectors remapped, etc. ) Move disk arm to requested cylinder Wait for proper sector to appear … OS abstraction return-code = read(fd, buff, nbytes) Operating Systems, summer 2016 10
UNIX high-level architecture User Interface Operating Systems, summer 2016 11
Operating Systems as Resource Managers q Multiple resources o Processors; Memory o Disks; Tapes; Printers o Network interfaces; Terminals q Controlled allocation of Resources among: o Groups, Users; Processes, Threads, … q Means of control: sharing/multiplexing/scheduling, monitoring, protection, report/payment Operating Systems, summer 2016 12
Introduction: outline q. What is an operating system? q. Some history q. OS concepts q. OS structure Operating Systems, summer 2016 13
History of Operating Systems q First generation 1945 - 1955 o vacuum tubes, plug boards – user plugs-in program Operating Systems, summer 2016 14
The first computers Electronic Numerical Integrator And Computer (ENIAC) Mathematical Analyzer, Numeric Integrator And Computer(MANIAC) Operating Systems, summer 2016 15
History of Operating Systems (cont’d) q Second generation 1955 - 1965 o transistors, batch systems – multiple programs on Disk q Third generation 1965 – 1980 o ICs and multiprogramming - user interaction (time-sharing) q Fourth generation 1980 – present o personal computers – graphic user-interface o Networks – file & computing services o Web-computing, Handheld devices , Cellular phones, Cloud computing… Operating Systems, summer 2016 16
How Bill Gates became rich… 1974: Intel releases the 8080 processor, needs an OS Please! develop an OS CP/M OS Gary Kildall Operating Systems, summer 2016 17
How Bill Gates became rich…(cont’d) 1974: Intel releases the 8080 processor, needs an OS CP/M OS Sure! Can you grant me CP/M rights? Gary Kildall Operating Systems, summer 2016 18
How Bill Gates became rich…(cont’d) 1980: IBM designs IMB PC, needs an OS Can you find an OS for our PC? So rry , t oo bu sy !!! !! Please meet IBM, they need an OS Gary Kildall Operating Systems, summer 2016 19
How Bill Gates became rich…(cont’d) 1980: IBM designs IMB PC, needs an OS Kildall too busy. Please develop an OS! I’de like to buy the DOS OS Sure, it’s yours for $75, 000 Operating Systems, summer 2016 20
How Bill Gates became rich…(cont’d) 1980: IBM designs IMB PC, needs an OS May I retain the rights for MSDOS? Sure, why not!! Operating Systems, summer 2016 21
How Bill Gates became rich…(cont’d) Well, this is 20: 20 hind vision… Operating Systems, summer 2016 22
Introduction: outline q. What is an operating system? q. Some history q. OS concepts q. OS structure Operating Systems, summer 2016 23
OS – Key Functions q Process management o process creation; deletion; suspension/preemption o process synchronization; communication; scheduling q Main-memory management o Manage used parts and their current users o Select processes to load from secondary storage o Allocate memory to running processes q Secondary storage management o Free-space management o Storage allocation Operating Systems, summer 2016 24
OS – Key Functions (cont’d) q File system management o File + directory - creation; deletion o File manipulation primitives o Mapping files onto secondary storage q I/O system management o General device-driver interface o Drivers for specific hardware devices q Protection system o Distinguish between authorized and unauthorized usage o Provide means of enforcement Operating Systems, summer 2016 25
Processes - a key concept q Resource container for “program in execution” q Timesharing, process suspension/preemption q Process Table q Process Groups q Signals Operating Systems, summer 2016 26
Why do we need multiple processes? • Single application: We want things to happen “concurrently” (E. g. : paging and typing in a text editor) • Multiple applications: processes running in the background (e. g. , Anti Virus) • Multiple users: The departmental computer; all types of Servers Operating Systems, summer 2016 27
Multiprogramming: how is it done? q CPU much faster than I/O o Computation/communication overlap q Memory large enough – requires memory protection! q Scheduler which manages flow of jobs in and out and shares CPU between jobs – requires Timer Operating Systems, summer 2016 28
Process trees • A process tree q A created two child processes, B and C q B created three child processes, D, E, and F Operating Systems, summer 2016 29
Inter-Process Communication (IPC) Two processes communicating via a pipe Operating Systems, summer 2016 30
Files: non volatile data q File types and operations on files q Directories - hierarchical structure q Working directories Operating Systems, summer 2016 31
Files: non volatile data (cont’d) q Protection and Security Unix - user; group; other (rwx bits) q File descriptors (handles) q I/O as a special file q Block & Character special files q Standard input; output; error q Pipes q Links Operating Systems, summer 2016 32
I/O is performed in kernel mode q All I/O instructions are privileged instructions q I/O devices and CPU can execute concurrently q CPU moves data between main memory and device controllers' buffers (done by device drivers) q Device controllers interrupt upon completion q Interrupts or Traps enable mode switching q Operating systems are interrupt-driven q Traps/signals: software interrupts Operating Systems, summer 2016 33
Interrupts and the fetch-decode-execute loop Do forever{ IR = memory[PC]; execute(IR); PC++; ! c i st If(Interrupt_Request) { i l p m i memory[0] = PC; S PC = memory[1] } } q An interrupt is an asynchronous event q The kernel interrupt handling routine may use a disable_interrupts instruction to avoid losing data while processing an interrupt request q Interrupt handler is typically called indirectly via the interrupt vector Operating Systems, summer 2016 34
Synchronous vs. Asynchronous I/O execute Operating Systems, summer 2016 35
Steps in Making a System Call There are 11 steps in making the system call: read (fd, buffer, nbytes) Is this call Synchronous or Asynchronous? Operating Systems, summer 2016 36
System Calls processes files directories miscellaneous Operating Systems, summer 2016 37
The Shell Command Language q sort < file 1 > file 2 q cat file 1 | sort | lpr • The Shell is a process which executes its commands as offspring processes • Processes may call shell commands by using the “system” system call Operating Systems, summer 2016 38
Shell structure – Parent & child A stripped-down shell: while (TRUE) { type_prompt( ); read_command (command, parameters) if (fork() > 0) { /* Parent code */ wait(); } else { /* Child code */ execvp (command, parameters); } /* repeat forever */ /* display prompt */ /* input from terminal */ /* fork off child process */ /* wait for child to exit */ /* execute command */ } Operating Systems, summer 2016 39
Linux Shell initialization q The init program (process 1) runs getty on all ports q Upon detecting a terminal, getty runs login q Typing in a user name and a password – login checks the passwd file and if correct runs a shell – the one specified in the UID entry q The shell is run with that user ID environment parameters Operating Systems, summer 2016 40
Running user commands q User types: ‘grep some_word file_name’ q Shell parses the command, inserts the strings grep, some_word, file_name into argv and their number to argc q Next, the shell uses fork() to create a process (same user ID) q Now, it takes the executable name grep and the arguments, all from argv, and uses execvp() (or a similar system call) to run the grep executable q On foreground execution, the shell would use the wait() system call and continue its session only after the child process terminates Operating Systems, summer 2016 41
UNIX Utility Programs A few of the more common UNIX utility programs required by POSIX Operating Systems, summer 2016 42
Introduction: outline q. What is an operating system? q. Some history q. OS concepts q. OS structure ( )חומר העשרה Operating Systems, summer 2016 43
Operating system structure 1. Monolithic systems 2. Virtual machines 3. Client-server model … Operating Systems, summer 2016 44
Monolithic systems have little structure Main procedure for invoking OS service Service Routines Utility procedures Operating Systems, summer 2016 45
Monolithic systems q Service routines are system calls q Utility procedures serve multiple service routines q All compiled into a single system Operating Systems, summer 2016 46
Virtual Machines q Provide an interface identical to the underlying bare machine q VM monitor creates multiple VMs, each executing on its own (virtual) processor and its own (virtual) memory q Virtual machines provide complete protection of system resources - even separate resources q Difficult to implement, due to the effort required to provide an exact duplicate of the underlying machine q Well-known examples: o MS-DOS on top of Windows o JVM o VMWare Operating Systems, summer 2016 47
Virtual Machines: IBM 370 user CMS CMS kernel VM/370 bare hardware CMS: Conversational Monitor System, a single user OS Operating Systems, summer 2016 48
Virtual Machines (cont’d) Operating Systems, summer 2016 49
Modern virtual machines q Different legacy servers run on different OS q Host sharing for web servers q Use multiple operating systems on a single machine q Security through isolation Operating Systems, summer 2016 50
Microkernels q Small number of lines of code mostly in C q Catching interrupts and switching processes in Assembly q C code manages and schedules processes, interprocess communication, i/o interaction q Offers few (~40) system calls for the rest of OS q Device drivers (Disk, Network, …) in user mode q Upper level contains Servers – File, Process. . Operating Systems, summer 2016 51
Client-Server Model Client Process . . . File Server Memory Server (Micro)Kernel . . Machine 1 Machine 2 Client File Server Kernel Network Machine 4 Machine 3 Process Server Kernel . . . Distributed System Operating Systems, summer 2016 52
Client/server architecture: Mechanism vs. Policy q Simple Kernel - modularity; minimal “privileged” operation q Servers for files, memory, etc. - distribution; user mode operation q good for distributed systems q Mechanism in kernel - how to do things. . q Policy outside - decide what to do; can be changed later. . q Critical servers in kernel – i/o disk server & the Scheduler – who serves who…. Operating Systems, summer 2016 53
- Zivan zabar
- Rfc 3031
- Sel-3031
- Rfc 3031
- Example of operating system.
- Evolution of operating systems
- Components of an operating system
- User view and system view in os
- Wsn operating systems
- Three easy pieces
- Operating system lab
- Open source operating system
- Tanenbaum operating systems
- File management in operating system
- Design issues of distributed file system
- Early operating systems
- Real-time operating systems
- Can we make operating systems reliable and secure
- Alternative operating systems
- Exo os
- Operating system internals and design principles
- Evolution of operating systems
- Examples of network operating systems
- Purchase msdn subscription
- Hobby operating systems
- Real time operating system characteristics
- Operating systems concepts
- Understanding operating systems
- Rootkit
- Software is
- Structures of operating system
- Components of operating system
- What is operating system architecture
- Module 4 operating systems and file management
- Modern operating systems 3rd edition
- Uc berkeley operating systems
- Operating systems
- Improving the reliability of commodity operating systems
- Overview of operating systems
- Operating systems
- Operating systems
- Tanenbaum structured computer organization
- Operating system chapter 5
- Mit operating systems
- Advanced operating system notes
- Types of operating systems
- Section 6 operating systems
- Section 6 operating systems
- Operating systems structure
- Operating systems overview
- Operating systems: internals and design principles
- Operating systems: internals and design principles
- Operating systems: internals and design principles
- Challenges of emerging trends in operating systems