Introduction to Operating Systems Part I

Transcription

1 TDDD63 Introduction to Operating Systems Part I Christoph Kessler IDA, Linköping University Copyright Notice: The slides partly use material from Silberschatz s, Galvin s and Gagne s book ( Operating System Concepts, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University. Christoph Kessler, IDA, Linköpings universitet.

2 Why should I be interested in Operating Systems? Mainframe OS/360 IBM 360 Midframe TOPS-10 DEC-20 MiniComputers Unix Workstations MS-DOS Windows Linux MacOSX Sun Workstations IBM PC? 2

3 A Whole New World! Smart Phones Wearable Devices Portability Connectivity Networks Sensors 3

4 A Whole New Future World! Smart Vehicles Smart Highways The current 7- Series BMW and S-class Mercedes boast about 100 processors apiece. A relatively lowprofile Volvo still has 50 to 60 baby processors on board. Smart Cities Smart Homes / Smart El-Grids 4

5 Increase in Hardware Complexity Moore s Law (prediction 1965): #Transistors / mm 2 doubles every ~2 years. Still holds today! Source: Intel Need for new types of interfacing to hardware Multiprocessor servers Hardware multithreading Multicore CPUs Many-Core CPUs Accelerators e.g. GPGPU Hybrid computing Clusters Cloud servers Nvidia Tesla GPU NSC s cluster supercomputer Triolith (TDDC78) 5

6 Increase in Software Complexity Need for new types of OS Architectures MacOS X 10.4: 86M LOC (2005) Linux kernel 2001 Linux kernel

7 Agenda Lecture I: Computer Systems Overview Building and Executing Programs Operating System Basics Lecture II: Interrupts and I/O System Calls CPU Management Memory Management File System Protection and Security 7

8 Computer Systems Overview Copyright Notice: The slides partly use material from Silberschatz s, Galvin s and Gagne s book ( Operating System Concepts, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University. Christoph Kessler, IDA, Linköpings universitet.

9 Computer Systems and Environments Stand-alone desktop computer Client-server systems Parallel systems Clustered systems Distributed systems Real-time systems Handheld systems 9

10 Stand-alone desktop computer PC, workstation: Computer system dedicated mainly to a single user. I/O devices: keyboards, mice, screens, small printers. Requirement: User convenience and responsiveness. Can adopt technology developed for larger operating system May run several different types of operating systems (Windows, MacOS, UNIX, Linux) 10

11 Client-Server Computing Servers respond to requests by clients Remote procedure call also across machine boundaries via network Client/Server are mainly software roles, but machines can be dedicated to one or few such roles, e.g. Compute server: compute an action requested by the client File server: Interface to file system (read, create, update, delete) 11

12 Parallel Systems (1) Multiprocessor systems with more than one CPU in close communication. Today the default, even for desktop machines (multi-core) Tightly coupled system (aka. shared-memory system, multiprocessor) processors share memory and a clock; communication usually takes place through the shared memory. Advantages of parallel systems: Increased throughput Economical Scalability of performance Multiprocessor system vs multiple single-processor system (reduction of hardware such as disks, controllers etc) Increased reliability graceful degradation (fault tolerance, ) fail-soft systems (replication, ) 12

13 Parallel Systems (2) Symmetric multiprocessing (SMP) Each processor runs an identical copy of the operating system. Many processes can run at once without performance deterioration. Most modern operating systems support SMP SMP architecture Asymmetric multiprocessing Each processor is assigned a specific task; a master processor schedules and allocates work to slave processors. More common in special-purpose systems (e.g., embedded MP-SoC) Remark: the notion of processor is relative: A traditional PC is normally considered to only have one CPU, but it usually has a graphics processor, a communication processor etc, and this is not considered a multi-processing system. 13

14 Hardware Multithreading, Multi-Core P0 P1 L1$ D1$ L1$ D1$ L2$ Memory Ctrl 2 hardware threads per core 2 cores per CPU chip Appears to the OS like 4 standard processors Main memory Intel Xeon Dualcore(2005) 14

15 Parallel Systems (3) Speed-up of a single application by parallel processing? Requires parallelisation / restructuring of the program Or explicitly parallel algorithms Used in High-Performance Computing for numerically intensive applications (weather forecast, simulations,...) Now ubiquitous problem due to switch to multicore/manycore CPUs Multicomputer ( distributed memory parallel computer ) loosely coupled can be a more economic and scalable alternative to SMP s but more cumbersome to program (message passing) Example: Beowulf Clusters More in TDDC78 Programming parallel computers NSC Triolith 15

16 Parallel Computing Systems 16

17 Clustered Systems Like multiprocessor systems, but multiple systems (servers) working together Often using a high-speed interconnect between servers (e.g. Infiniband) Usually sharing external mass storage via a storage-area network (SAN) Provides a high-availability/reliability service which survives failures Asymmetric clustering - one server runs the application while other servers are in hot-standby mode Symmetric clustering - has multiple nodes running the same application, monitoring each other Some clusters are used for high-performance computing (HPC) Applications must be written to use parallelization HPC clusters: MPI (Message-Passing Interface) TDDC78 Data centers: Mapreduce / Hadoop NSC Triolith 17

18 Distributed Systems (1) Loosely coupled system each processor has its own local memory processors communicate with one another through various communications lines, such as high-speed buses or telephone lines (LAN, WAN, MAN, Bluetooth, ). Distribute the computation among several physical processors. Advantages of distributed systems: Resource sharing Computation speed up Adaptivity: load sharing (migration of jobs) Fault tolerance May be either client-server or peer-to-peer systems 18

19 Distributed Systems (2) Network Operating System provides file sharing, e.g., NFS - Network File System provides communication scheme runs independently from other computers on the network Distributed Operating System less autonomy between computers gives the impression that there is a single operating system controlling the network. More about this in TDDD25 Distributed Systems 19

20 Distributed Computing Systems 20

21 Real-Time Systems Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Well-defined tasks with fixed time constraints. Hard real-time systems. Conflicts with time-sharing systems, not supported by general-purpose OSs. Soft real-time systems Limited utility in industrial control or robotics Useful in applications (multimedia, virtual reality) requiring advanced OS features. More in TDDD07 Real-time Systems 21

22 Handheld Systems Personal Digital Assistants (PDAs), ipads etc. Cellular telephones Issues: Limited memory Slow processors Small display screens Limited battery lifetime Iphone 5S Shipping with 2GB-4GB RAM? GHz 22

23 Before talking about Operating Systems Copyright Notice: The slides partly use material from Silberschatz s, Galvin s and Gagne s book ( Operating System Concepts, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University. Christoph Kessler, IDA, Linköpings universitet.

24 Before talking about OS, a short note on programming languages suitable for system programming Early operating systems were implemented in assembly language (and some low-level parts of modern OS still are). Necessary for direct access to hardware devices Since the 1970s the dominating language for system programming is C. Also used a lot in high-performance and embedded computing Today, no new microprocessor ships without a C compiler. Many high-level programming languages are compiled to C. You will need C for programming labs in later courses Operating systems, Compiler construction, Parallel programming, Multicore/GPU programming, Realtime systems, Embedded systems, 24

25 Java vs. C Java C For application programming only Design goals: Programmer productivity Safety Hardware completely hidden Comfortable E.g. automatic memory management Protection (to some degree) Slow E.g., array bound checking Time-unpredictable For system programming mainly Design goals: Direct control of hardware High performance / real-time Minimalistic design Less comfortable Little protection low-level 25

26 A Short History of C C was developed in the early 1970 s by Dennis Ritchie at Bell Labs Objective: structured but flexible programming language e.g. for writing device drivers or operating systems Used for implementing the Unix OS Book 1978 by Brian Kernighan and Dennis Ritchie ( K&R-C ) ANSI-C 1989 standard by ANSI ( C89 ) The C standard for many programmers (and compilers...) Became the basis for standard C++ Java borrowed much of its syntax The GNU C compiler implemented a superset ( GNU-C ) C99 standard by ISO, only minor changes C11 (ISO) multithreading support added 26

27 How to build and execute programs on a real computer Copyright Notice: The slides partly use material from Silberschatz s, Galvin s and Gagne s book ( Operating System Concepts, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University. Christoph Kessler, IDA, Linköpings universitet.

28 The Compilation Workflow /* file hello.c */ #include <stdio.h> int main() { printf("hello, world\n"); }.file "hello.c".section.rodata.str1.1,"ams",@progbits,1.lc0:.string "hello, world".text.p2align 4,,15.globl main.type main: pushl%ebp movl %esp, %ebp subl $8, %esp andl $-16, %esp subl $16, %esp movl $.LC0, (%esp) call puts leave xorl %eax, %eax ret size 28

29 Preprocessing Phase C Preprocessor (cpp): modifies the original C source program according to directives that begin with the # character. #include <stdio.h> tells the processor to read the contents of the system header file stdio.h and insert it directly into the program text. Output is another C source program, typically with the.i suffix. 29

30 Compilation Phase Compilation Phase (cc1): Translate the text file hello.i into the text file hello.s. hello.s contains an assembly-language program Each statement in an assembly language program exactly describes one low-level machine language instruction in a standard text form. C compiler Assembly language Fortran compiler Assembly language provides a common output language for different compilers main: pushl movl subl andl subl movl call leave xorl ret %ebp %esp, %ebp $8, %esp $-16, %esp $16, %esp $.LC0, (%esp) puts %eax, %eax 30

31 hello.s (in x86 assembler language).file "hello, world".text.p2align 4,,15.globl main.type main: pushl %ebp movl %esp, %ebp subl $8, %esp andl $-16, %esp subl $16, %esp movl $.LC0, (%esp) call puts leave xorl%eax, %eax ret.size "GCC: (GNU) (Red Hat fc3)" 31

32 Assembly Phase Assembler (as): translates the text-based assembly program into machine language instructions, packages them in a form known as a relocatable object program, and stores the result in the object file hello.o hello.o is a binary file (object file) whose bytes encode machine instructions and -data rather than characters. Binary files use a system-specific binary file format, e.g. ELF, COFF. a4 f0 dd 07 7c 65 a6 b2 06 0f c3 dd a2 ff bd 87 32

33 Linking Phase Linker (ld): merges pre-compiled object files to a single one. The result is an executable object file that is ready to be loaded into memory (using the OS loader) and executed by the system. The hello program uses the printf function, which is part of the standard C library. This function resides in a separate precompiled object file (e.g. printf.o or in libc.a) that has to be merged with hello.o. Also some additional code and data (program startup code, C runtime system, etc., in libc.a) is added by the linker. 33

34 Calling the entire toolchain E.g., gcc hello.c o hello (here, for the GNU C compiler gcc) calls cpp, cc1, as, ld for single-module program hello.c For automatizing the build process of multi-module programs, building-tools like make or IDEs like ECLIPSE are convenient. 34

35 Compiling and Linking for Multi-Module C Programs xy.h glob.h stdio.h #include #include #include abc.c preprocess compile + asm mymain.c def.c abc.o mymain.o def.o link a.out (executable) libc.a C run-time library is linked with the user code 35

36 Running an Executable Program /* hello.c */ #include <stdio.h> int main() { printf("hello, world\n"); } In a Unix system, a shell is an application program which is a command line interpreter The shell prints a prompt, waits for the user to type in a command and then performs the command. unix>./hello Input Preprocess Compile Assemble Link hello, world unix> Output hello Executable Object File (binary) If it is not a built-in shell command, then the shell assumes it is an executable file and that it should load and run it. 36

37 Running the hello Program As the characters./hello are typed at the keyboard, the shell program reads each one into a register and then it is stored in memory Reading the hello command from the keyboard 37

38 Running the hello program When the enter key is hit on the keyboard, the shell knows that we have finished typing the command. The shell then calls the OS to allocate memory and load the executable file. The loader copies the code and data in the hello object file from disk to main memory. Loading the executable from disk into main memory Using a technique called Direct Memory Access (DMA) the data travels directly from the disk to the main memory without passing through the processor. 38

39 Running the hello program Writing the output string from memory to the display Once the code and data in the hello object file are loaded into memory, the processor begins executing the machine instructions in the hello program s main routine main: pushl %ebp movl %esp, %ebp subl $8, %esp andl $-16, %esp subl $16, %esp movl $.LC0, (%esp) call puts leave xorl %eax, %eax ret These instructions copy the bytes in the hello, world string from memory to the register file and from there to the display device where they are displayed on the screen 39

40 OS Basics Copyright Notice: The slides partly use material from Silberschatz s, Galvin s and Gagne s book ( Operating System Concepts, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University. Christoph Kessler, IDA, Linköpings universitet.

41 What is an Operating System (OS)? A program that acts as an intermediary between a user of a computer and the computer hardware. Operating system goals: Execute user programs in a well-defined environment. Make application software portable and not tied to a specific machine hiding low-level and implementational detail Make the computer system convenient to use. Administrate system resources. Improves overall system reliability error confinement, fault tolerance, reconfiguration... Enable efficient use of the computer hardware support parallel activity, avoid wasted CPU cycles... Provides protection mechanisms for user programs and files and security against possible threats from within and outside the system 41

42 What is an Operating System (OS)? An operating system provides an environment within which other programs can do useful work; the OS does not perform any useful function itself. 42

43 Where are OSs found? General purpose systems Embedded systems Microprocessor market shares in % 1% 43

44 Operating Systems (A Selection) General purpose operating systems Unix incl. variants, such as Sun/Oracle Solaris, HP-UX Linux Windows 95/98/2000, NT/XP/Vista/7/8/10/ Mac OS X Application specific operating systems, e.g. mobile OS, real-time OS Android ios Symbian Windows CE, Mobile, Phone Embedded Linux RT-Linux VxWorks OSE QNX... 44

45 Operating System Definition OS is a resource allocator Manages all resources of a computer system Decides between conflicting requests for efficient and fair resource use OS is a control program Controls execution of programs to prevent errors and improper use of the computer No universally accepted definition The one program running at all times on the computer is called the kernel. Everything else is either a system program (ships with the operating system) or an application program. 45

46 Computer System Structure Computer system can be divided into 4 components: Hardware provides basic computing resources CPU, memory, I/O devices Operating system controls and coordinates use of hardware among various applications and users Application programs define the ways in which the system resources are used to solve the computing problems of the users Word processors, compilers, web browsers, database systems, games Users People, machines, other computers 46

47 Agenda Lecture I: Computer Systems Overview Building and Executing Programs Operating System Basics Lecture II: Interrupts and I/O System Calls CPU Management Memory Management File System Protection and Security 47