Introduction to Operating Systems PDF

Introduction to Operating Systems Chapter 1  Class outline Introduction, concepts, review & historical perspective Processes Synchronization Scheduling Deadlock Memory management, address translation, and virtua...

Introduction to Operating Systems Chapter 1  Class outline Introduction, concepts, review & historical perspective Processes Synchronization Scheduling Deadlock Memory management, address translation, and virtual memory Operating system management of I/O File systems Security & protection Distributed systems (as time permits) CS 1550, cs.pitt.edu) Chapter 1 2  Overview: Chapter 1 What is an operating system, anyway? Operating systems history The zoo of modern operating systems Review of computer hardware Operating system concepts Operating system structure User interface to the operating system Anatomy of a system call Chapter 1 3  What is an operating system? A program that runs on the “raw” hardware and supports Resource Abstraction Resource Sharing Abstracts and standardizes the interface to the user across different types of hardware Virtual machine hides the messy details which must be performed Manages the hardware resources Each program gets time with the resource Each program gets space on the resource May have potentially conflicting goals: Use hardware efficiently Give maximum performance to each user Chapter 1 4  Operating system timeline First generation: 1945 – 1955 Vacuum tubes Plug boards Second generation: 1955 – 1965 Transistors Batch systems Third generation: 1965 – 1980 Integrated circuits Multiprogramming Fourth generation: 1980 – present Large scale integration Personal computers Next generation: ??? Systems connected by high-speed networks? Wide area resource management? Chapter 1 5  First generation: direct input Run one job at a time Enter it into the computer (might require rewiring!) Run it Record the results Problem: lots of wasted computer time! Computer was idle during first and last steps Computers were very expensive! Goal: make better use of an expensive commodity: computer time Chapter 1 6  Second generation: batch systems Bring cards to 1401 Read cards onto input tape Put input tape on 7094 Perform the computation, writing results to output tape Put output tape on 1401, which prints output Chapter 1 7  Structure of a typical 2nd generation job Data for $END program FORTRAN $RUN $LOAD program $FORTRAN $JOB, 10,6610802, ETHAN MILLER Chapter 1 8  Spooling Original batch systems used tape drives Later batch systems used disks for buffering Operator read cards onto disk attached to the computer Computer read jobs from disk Computer wrote job results to disk Operator directed that job results be printed from disk Disks enabled simultaneous peripheral operation on- line (spooling) Computer overlapped I/O of one job with execution of another Better utilization of the expensive CPU Still only one job active at any given time Chapter 1 9  Third generation: multiprogramming Multiple jobs in memory Protected from one another Job 3 Operating system protected from each job as well Job 2 Resources (time, hardware) Memory split between jobs partitions Job 1 Still not interactive User submits job Computer runs it Operating User gets results minutes system (hours, days) later Chapter 1 10  Timesharing Multiprogramming allowed several jobs to be active at one time Initially used for batch systems Cheaper hardware terminals -> interactive use Computer use got much cheaper and easier No more “priesthood” Quick turnaround meant quick fixes for problems Chapter 1 11  Types of modern operating systems Mainframe operating systems: MVS Server operating systems: FreeBSD, Solaris Multiprocessor operating systems: Cellular IRIX Personal computer operating systems: Windows, Unix Real-time operating systems: VxWorks Embedded operating systems Smart card operating systems  Some operating systems can fit into more than one category Chapter 1 12  Components of a simple PC Outside world Video Hard drive USB Network controller controller controller controller CPU Computer internals (inside the “box”) Memory Chapter 1 13  CPU internals Execute Fetch Decode unit unit unit Fetch Decode Execute Execute Buffer unit unit unit unit Fetch Decode unit unit Execute unit Pipelined CPU Superscalar CPU Chapter 1 14  Storage pyramid Capacity Access latency < 1 KB Registers 1 ns Better 1 MB Cache (SRAM) 2–5 ns 256 MB Main memory (DRAM) 50 ns 40 GB Magnetic disk 5 ms Better > 1 TB Magnetic tape 50 sec Goal: really large memory with very low latency Latencies are smaller at the top of the hierarchy Capacities are larger at the bottom of the hierarchy Solution: move data between levels to create illusion of large memory with low latency Chapter 1 15  Disk drive structure head Data stored on surfaces Up to two surfaces per platter sector One or more platters per disk Data in concentric tracks platter Tracks broken into sectors 256B-1KB per sector track Cylinder: corresponding tracks on all surfaces cylinder Data read and written by heads surfaces Actuator moves heads Heads move in unison spindle actuator Chapter 1 16  Memory Address Address 0x2ffff 0x2ffff User program User data 0x2d000 and data 0x2b000 0x2bfff Limit2 User data 0x27fff Limit 0x29000 Base2 User program 0x24fff Limit1 and data User program 0x23000 Base 0x23000 Base1 0x1dfff 0x1dfff Operating Operating system system 0 0 Single base/limit pair: set for each process Two base/limit registers: one for program, one for data Chapter 1 17  Anatomy of a device request Instructionn 3 2 Instructionn+1 1: Interrupt 5 Interrupt Disk CPU controller controller 1 6 4 Operating system 3: Return Interrupt handler Left: sequence as seen by hardware 2: Process interrupt Request sent to controller, then to disk Disk responds, signals disk controller which tells interrupt controller Interrupt controller notifies CPU Right: interrupt handling (software point of view) Chapter 1 18  Operating systems concepts Many of these should be familiar to Unix users… Processes (and trees of processes) Deadlock File systems & directory trees Pipes We’ll cover all of these in more depth later on, but it’s useful to have some basic definitions now Chapter 1 19  Processes Process: program in execution Address space (memory) the A program can use State (registers, including program counter & stack pointer) B C D OS keeps track of all processes in a process table Processes can create other processes Process tree tracks these E F G relationships A is the root of the tree A created three child processes: B, C, and D C created two child processes: E and F D created one child process: G Chapter 1 20  Inside a (Unix) process 0x7fffffff Processes have three Stack segments Text: program code Data: program data Statically declared variables Areas allocated by malloc() or new Stack Automatic variables Data Procedure call information Data Address space growth Text: doesn’t grow Text Data: grows “up” Stack: grows “down” 0 Chapter 1 21 Deadlock Potential deadlock Actual deadlock Chapter 1 22  Hierarchical file systems Root directory bin cse faculty grads ls ps cp csh elm sbrandt kag amer4 classes research stuff stuff Chapter 1 23  Interprocess communication Processes want to exchange information with each other Many ways to do this, including Network Pipe (special file): A writes into pipe, and B reads from it A B Chapter 1 24  System calls Programs want the OS to perform a service Access a file Create a process Others… Accomplished by system call Program passes relevant information to OS OS performs the service if The OS is able to do so The service is permitted for this program at this time OS checks information passed to make sure it’s OK Don’t want programs reading data into other programs’ memory! Chapter 1 25  Making a system call 0xffffffff Library System call: (read call) read(fd,buffer,length) Program pushes arguments, Return to caller Trap to kernel calls library 3 Trap code in register Library sets up trap, calls User OS space 8 2 OS handles system call 4 Increment SP 9 7 Control returns to library Call read Library returns to user 1 Push arguments program User Kernel code 5 6 Sys call space Dispatch handler (OS) 0 Chapter 1 26  System calls for files & directories Call Description fd = open(name,how) Open a file for reading and/or writing s = close(fd) Close an open file n = read(fd,buffer,size) Read data from a file into a buffer n = write(fd,buffer,size) Write data from a buffer into a file s = lseek(fd,offset,whence) Move the “current” pointer for a file s = stat(name,&buffer) Get a file’s status information (in buffer) s = mkdir(name,mode) Create a new directory s = rmdir(name) Remove a directory (must be empty) s = link(name1,name2) Create a new entry (name2) that points to the same object as name1 s = unlink(name) Remove name as a link to an object (deletes the object if name was the only link to it) Chapter 1 27  More system calls Call Description pid = fork() Create a child process identical to the parent pid=waitpid(pid,&statloc,options) Wait for a child to terminate s = execve(name,argv,environp) Replace a process’ core image exit(status) Terminate process execution and return status s = chdir(dirname) Change the working directory s = chmod(name,mode) Change a file’s protection bits s = kill(pid,signal) Send a signal to a process seconds = time(&seconds) Get the elapsed time since 1 Jan 1970 Chapter 1 28  A simple shell while (TRUE) { type_prompt( ); read_command (command, parameters) if (fork() != 0) { waitpid( -1, &status, 0); } else { execve (command, parameters, 0); } } Chapter 1 29 Monolithic OS structure Main procedure Service routines Utility routines Chapter 1 30  Virtual machines App1 App2 App3 System calls Linux Windows NT FreeBSD I/O instructions VMware VMware VMware Calls to simulate I/O Linux “Real” I/O instructions Bare hardware First widely used in VM/370 with CMS Available today in VMware Allows users to run any x86-based OS on top of Linux or NT “Guest” OS can crash without harming underlying OS Only virtual machine fails—rest of underlying OS is fine “Guest” OS can even use raw hardware Virtual machine keeps things separated Chapter 1 31  Microkernels (client-server) Client Client Process Terminal File Memory process process server server … server server User mode Microkernel Kernel mode Processes (clients and OS servers) don’t share memory Communication via message-passing Separation reduces risk of “byzantine” failures Examples include Mach Chapter 1 32  Metric units Exp. Number Prefix Exp. Number Prefix 10-3 0.001 milli 103 1,000 Kilo 10-6 0.000001 micro 106 1,000,000 Mega 10-9 0.000000001 nano 109 1,000,000,000 Giga 10-12 0.000000000001 pico 1012 1,000,000,000,000 Tera 10-15 0.000000000000001 femto 1015 1,000,000,000,000,000 Peta 10-18 0.000000000000000001 atto 1018 1,000,000,000,000,000,000 Exa Chapter 1 33