Operating Systems. Minati De. Lecture 1: Introduction. Department of Mathematics, Indian Institute of Technology Delhi, India.

Transcription

1 Operating Systems Minati De Department of Mathematics, Indian Institute of Technology Delhi, India. Lecture 1: Introduction

2 Course Logistics Text Books: Operating Systems: Principles and Practice 2nd Edition Thomas Anderson, Michael Dahlin Operating Systems: Three Easy Pieces Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau Weightage Assignments: 20%; Minor1: 15%; Minor2: 15%; Surprise Quiz: 15%; Major: 35%

3 Course Logistics Text Books: Operating Systems: Principles and Practice 2nd Edition Thomas Anderson, Michael Dahlin Operating Systems: Three Easy Pieces Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau Other References: The Design of the UNIX Operating System (Prentice Hall) M.J. Bach Advanced Programming in the UNIX Environment (Addison Wesley) W. Richard Stevens and Stephen A. Rago Weightage Assignments: 20%; Minor1: 15%; Minor2: 15%; Surprise Quiz: 15%; Major: 35%

4 Course Logistics Text Books: Operating Systems: Principles and Practice 2nd Edition Thomas Anderson, Michael Dahlin Operating Systems: Three Easy Pieces Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau Other References: The Design of the UNIX Operating System (Prentice Hall) M.J. Bach Advanced Programming in the UNIX Environment (Addison Wesley) W. Richard Stevens and Stephen A. Rago TAs: Kapil Ahuja Sahil Bhatnagar Weightage Assignments: 20%; Minor1: 15%; Minor2: 15%; Surprise Quiz: 15%; Major: 35%

5 Course Logistics Text Books: Operating Systems: Principles and Practice 2nd Edition Thomas Anderson, Michael Dahlin Operating Systems: Three Easy Pieces Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau Other References: The Design of the UNIX Operating System (Prentice Hall) M.J. Bach Advanced Programming in the UNIX Environment (Addison Wesley) W. Richard Stevens and Stephen A. Rago TAs: Kapil Ahuja Sahil Bhatnagar Course webpage: web.iitd.ac.in/ minati/mtl458/ Weightage Assignments: 20%; Minor1: 15%; Minor2: 15%; Surprise Quiz: 15%; Major: 35%

6 What is an Operating Syetem? Operating Syetem Software to manage a computer s resources for its users and applications APP APP APP Operating System Hardware

7 What is an Operating Syetem? Operating Syetem Software(set of programs + a library of functions) to manage a computer s resources for its users and applications Users User-mode Kernel-mode APP APP APP System System System Library Library Library Kernel-user Interface (Abstract virtual machine) File System Virtual Memory TCP/IP Networking Scheduling Operating systems are among the most complex pieces of software yet developed, William Stallings, 1994 Hardware Disk Hardware Abstraction Layer Hardware-Specific Software and Device Drivers Processors Address Translation Graphics Processor Network

8 Computer Organization

9 What happens when a program runs? A compiler translates high level programs into an executable (.c to a.out )

10 What happens when a program runs? A compiler translates high level programs into an executable (.c to a.out ) The exe contains instructions that the CPU can understand, and data of the program (all numbered with addresses)

11 What happens when a program runs? A compiler translates high level programs into an executable (.c to a.out ) The exe contains instructions that the CPU can understand, and data of the program (all numbered with addresses) Instructions run on CPU: hardware implements an instruction set architecture (ISA)

12 What happens when a program runs? A compiler translates high level programs into an executable (.c to a.out ) The exe contains instructions that the CPU can understand, and data of the program (all numbered with addresses) Instructions run on CPU: hardware implements an instruction set architecture (ISA) CPU also consists of a few registers, e.g., Pointer to current instruction (program counter or PC) Operands of instructions, memory addresses

13 What happens when a program runs?

14 What happens when a program runs? OS is Responsible for Making it easy to run programs Allowing programs to share memory Enabling programs to interact with devices OS is in charge of making sure the system operates correctly and efficiently.

15 Things to manage Memory - Loads program executable (code, data) from disk to memory

16 Things to manage Memory - Loads program executable (code, data) from disk to memory CPU - Initializes program counter (PC) and other registers to begin execution

17 Things to manage Memory - Loads program executable (code, data) from disk to memory CPU - Initializes program counter (PC) and other registers to begin execution Hard disk (File system) Read/write files from disk

18 Things to manage Memory - Loads program executable (code, data) from disk to memory CPU - Initializes program counter (PC) and other registers to begin execution Hard disk (File system) Read/write files from disk I/O devices

19 OS manages CPU OS provides the process abstraction

20 OS manages CPU OS provides the process abstraction Process: a running program

21 OS manages CPU OS provides the process abstraction Process: a running program OS creates and manages processes

22 OS manages CPU OS provides the process abstraction Process: a running program OS creates and manages processes Each process has the illusion of having the complete CPU, i.e., OS virtualizes CPU

23 OS manages CPU OS provides the process abstraction Process: a running program OS creates and manages processes Each process has the illusion of having the complete CPU, i.e., OS virtualizes CPU Timeshares CPU between processes

24 OS manages CPU OS provides the process abstraction Process: a running program OS creates and manages processes Each process has the illusion of having the complete CPU, i.e., OS virtualizes CPU Timeshares CPU between processes Enables coordination between processes

25 OS manages Memory OS manages the memory of the process: code, data, stack, heap etc Code Data Stack Heap

26 OS manages Memory OS manages the memory of the process: code, data, stack, heap etc Each process thinks it has a dedicated memory space for itself, numbers code and data starting from 0 (virtual addresses) Code Data Stack Heap

27 OS manages Memory OS manages the memory of the process: code, data, stack, heap etc Each process thinks it has a dedicated memory space for itself, numbers code and data starting from 0 (virtual addresses) OS abstracts out the details of the actual placement in memory, translates from virtual addresses to actual physical addresses

28 OS manages I/O devices OS has code to manage disk, network card, and other external devices: device drivers Device driver talks the language of the hardware devices Issues instructions to devices (fetch data from a file) Responds to interrupt events from devices (user has pressed a key on keyboard) Persistent data organized as a filesystem on disk

29 Design goals of an operating system Convenience, abstraction of hardware resources for user programs

30 Design goals of an operating system Convenience, abstraction of hardware resources for user programs Efficiency of usage of CPU, memory, etc.

31 Design goals of an operating system Convenience, abstraction of hardware resources for user programs Efficiency of usage of CPU, memory, etc. Isolation between multiple processes

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33 Primary intersection point OS is the point where hardware, software, programming languages, data structures, and algorithms all come together

34 Primary intersection point OS is the point where hardware, software, programming languages, data structures, and algorithms all come together Curiosity look under the hood

35 Primary intersection point OS is the point where hardware, software, programming languages, data structures, and algorithms all come together Curiosity look under the hood Increasing need for specialized operating systems. e.g. embedded operating systems for devices - cell phones, sensors and controllers real-time operating systems - aircraft control, multimedia

36 Course Logistics OS is everywhere M. De Operating Systems

37 OS History MVS Multics MS/DOS VMS VM/370 UNIX Windows BSD UNIX Mach Windows NT VMWare Linux NEXT MacOS Windows 8 MacOS X Influence Descendant Android ios

38 Computer 1.3 Operating Performance Systems: Past, Over Present, Time and Future Factor (2014/1981) Uniprocessor speed (MIPS) K CPUs per computer Processor MIPS/$ $100K $25 $ K DRAM Capacity (MiB)/$ K 500K Disk Capacity (GiB)/$ K 10M Home Internet 300 bps 256 Kbps 20 Mbps 100K 10 Mbps 100 Mbps 10 Gbps Machine room network 1000 (shared) (switched) (switched) Ratio of users to computers 100:1 1:1 1:several 100+

39 Course Logistics Early Operating Systems:Computers Very Expensive One application at a time Had complete control of hardware OS was runtime library Users would stand in line to use the computer M. De Operating Systems

40 Early Operating Systems:Computers Very Expensive Batch systems Keep CPU busy by having a queue of jobs OS would load next job while current one runs Users would submit jobs, and wait, and wait, and

41 Time-Sharing Operating Systems:Computers and People Expensive Multiple users on computer at same time Multiprogramming: run multiple programs at same time Interactive performance: try to complete everyone s tasks quickly As computers became cheaper, more important to optimize for user time, not computer time

42 Today s Operating Systems:Computers Cheap Today s Operating Systems Smartphones Embedded systems Laptops Tablets Virtual machines Data center servers

43 Tomorrow s Operating Systems Giant-scale data centers Increasing numbers of processors per computer Increasing numbers of computers per user Very large scale storage