1. OPERATING SYSTEMS
Introduction

2. Instructor and TA Instructor TA Dr. Yasser Fouad
Associate Professor, CS at Alexandria University
Course Page: TA

3. Course Description
Introduction to basic components in operating systems
Process management and coordination
Memory management
Storage management
Advanced topics (depending on schedule)
Distributed systems
Virtual machines
Case studies and recent developments

4. Outline & Schedule Basics (Ch. 1-2) Process management (Ch. 3-7)
Introduction
System structures
Process management (Ch. 3-7)
Process concept
Multithreaded programming
Process scheduling
Synchronization
Deadlocks
Memory management (Ch. 8-9)
Memory management strategies
Virtual memory management

5. Outline & Schedule (Cont’d)
Outline (cont’d)
Storage management (Ch )
File system
Secondary storage structure
I/O systems
System protection and security (Ch )
Case studies (Ch )
Linux, Windows 7, Influential OS
Reorganized and integrated throughout the text
Real-time systems
Storage management
Removed from International Student Edition and moved into “Advanced Topics” in 9th ed.
Virtual machines
Distributed systems

6. Recent Growth in Fundamental Areas
Multicore systems
Mobile computing
Virtualization

7. What is an Operating System?
A program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system goals:
Execute user programs and make solving user problems easier.
Make the computer system convenient to use.

8. OPERATING SYSTEM OVERVIEW
An interface between users and hardware - an environment "architecture”
Allows convenient usage
Allows efficient usage; parallel activity, avoids wasted cycles
Provides information protection
Gives each user a slice of the resources
Acts as a control program.

9. What is an operating system?
Special layer of software that provides application software access to hardware resources
Convenient abstraction of complex hardware devices
Protected access to shared resources
Security and authentication
Communication amongst logical entities

10. What Does an OS do? Provide abstractions to apps Manage resources:
File systems
Processes, threads
VM, containers
Naming system …
Manage resources:
Memory, CPU, storage, …
Achieves the above by implementing specific algos and techniques:
Scheduling
Concurrency
Transactions
Security
…..

11. OPERATING SYSTEM OVERVIEW
The Layers Of A System
OPERATING SYSTEM OVERVIEW
Humans
Program Interface
User Programs
O.S. Interface
O.S.
Hardware Interface/ Privileged Instructions
Disk/Tape/Memory

12. OPERATING SYSTEM OVERVIEW
Components
A mechanism for scheduling jobs or processes. Scheduling can be as simple as running the next process, or it can use relatively complex rules to pick a running process.
A method for simultaneous CPU execution and IO handling. Processing is going on even as IO is occurring in preparation for future CPU work.
Off Line Processing; not only are IO and CPU happening concurrently, but some off-board processing is occurring with the IO.

13. OPERATING SYSTEM OVERVIEW
Components
The CPU is wasted if a job waits for I/O. This leads to:
Multiprogramming ( dynamic switching ). While one job waits for a resource, the CPU can find another job to run. It means that several jobs are ready to run and only need the CPU in order to continue.
All of this leads to:
memory management
resource scheduling
deadlock protection
which are the subject of the rest of this course.

14. OPERATING SYSTEM OVERVIEW
Characteristics
Other Characteristics include:
Time Sharing - multiprogramming environment that's also interactive.
Multiprocessing - Tightly coupled systems that communicate via shared memory. Used for scientific applications. Used for speed improvement by putting together a number of off-the-shelf processors.
Distributed Systems - Loosely coupled systems that communicate via message passing. Advantages include resource sharing, speed up, reliability, communication.
Real Time Systems - Rapid response time is main characteristic. Used in control of applications where rapid response to a stimulus is essential.

15. OPERATING SYSTEM OVERVIEW
Characteristics
Interrupts:
Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines.
Interrupt architecture must save the address of the interrupted instruction.
Incoming interrupts are disabled while another interrupt is being processed to prevent a lost interrupt.
A trap is a software-generated interrupt caused either by an error or a user request.
An operating system is interrupt driven.

16. OPERATING SYSTEM OVERVIEW
Hardware
Support
These are the devices that make up a typical system.
Any of these devices can cause an electrical interrupt that grabs the attention of the CPU.

17. OPERATING SYSTEM OVERVIEW
Hardware
Support
Sequence of events for processing an IO request.
Comparing Synchronous and Asynchronous IO Operations

18. OPERATING SYSTEM OVERVIEW
Hardware
Support
This is O.S. Bookkeeping. These structures are necessary to keep track of IO in progress.

19. Computer-System Architecture
Most systems use a single general-purpose processor (PDAs through mainframes)
Most systems have special-purpose processors as well
Multiprocessors systems growing in use and importance
Also known as parallel systems, tightly-coupled systems
Advantages include
Increased throughput
Economy of scale
Increased reliability – graceful degradation or fault tolerance
Two types
Asymmetric Multiprocessing
Symmetric Multiprocessing

20. Symmetric Multiprocessing Architecture

21. A Dual-Core Design

22. Clustered Systems
Like multiprocessor systems, but multiple systems working together
Usually sharing storage via a storage-area network (SAN)
Provides a high-availability service which survives failures
Asymmetric clustering has one machine in hot-standby mode
Symmetric clustering has multiple nodes running applications, monitoring each other
Some clusters are for high-performance computing (HPC)
Applications must be written to use parallelization

23. OPERATING SYSTEM OVERVIEW
Storage
Hierarchy
Very fast storage is very expensive. So the Operating System manages a hierarchy of storage devices in order to make the best use of resources. In fact, considerable effort goes into this support.
Fast and Expensive
Slow an Cheap

24. OPERATING SYSTEM OVERVIEW
Storage
Hierarchy
Performance:

25. OPERATING SYSTEM OVERVIEW
Storage
Hierarchy
Caching:
Important principle, performed at many levels in a computer (in hardware, operating system, software)
Information in use copied from slower to faster storage temporarily
Faster storage (cache) checked first to determine if information is there
If it is, information used directly from the cache (fast)
If not, data copied to cache and used there
Cache smaller than storage being cached
Cache management important design problem
Cache size and replacement policy

26. OPERATING SYSTEM OVERVIEW
Protection
The goal is protecting the Operating System and others from malicious or ignorant users.
The User/Supervisor Mode and privileged instructions.
Concurrent threads might interfere with others. This leads to protection of resources by user/supervisor mode. These resources include:
I/O Define I/O instructions as privileged; they can be executed only in Supervisor mode. System calls get us from user to supervisor mode.

27. OPERATING SYSTEM OVERVIEW
Protection
Memory A user program can only access its own logical memory. For instance, it can't modify supervisor code. Depends on an address translation scheme such as that shown here.

28. Desktop Systems
Personal computers – computer system dedicated to a single user.
I/O devices – keyboards, mice, display screens, small printers.
User convenience and responsiveness.
Can adopt technology developed for larger operating system’ often individuals have sole use of computer and do not need advanced CPU utilization of protection features.
May run several different types of operating systems (Windows, MacOS, UNIX, Linux)

29. Parallel Systems
Multiprocessor systems with more than on CPU in close communication.
Tightly coupled system – processors share memory and a clock; communication usually takes place through the shared memory.
Advantages of parallel system:
Increased throughput
Economical
Increased reliability
graceful degradation
fail-soft systems

30. Parallel Systems (Cont.)
Symmetric multiprocessing (SMP)
Each processor runs and identical copy of the operating system.
Many processes can run at once without performance deterioration.
Most modern operating systems support SMP
Asymmetric multiprocessing
Each processor is assigned a specific task; master processor schedules and allocated work to slave processors.
More common in extremely large systems

31. Symmetric Multiprocessing Architecture

32. Distributed Systems
Distribute the computation among several physical processors.
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.
Advantages of distributed systems.
Resources Sharing
Computation speed up – load sharing
Reliability
Communications

33. Distributed Systems (cont)
Requires networking infrastructure.
Local area networks (LAN) or Wide area networks (WAN)
May be either client-server or peer-to-peer systems.

34. 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 fixed-time constraints.
Real-Time systems may be either hard or soft real-time.

35. Real-Time Systems (Cont.)
Hard real-time:
Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM)
Conflicts with time-sharing systems, not supported by general-purpose operating systems.
Soft real-time
Limited utility in industrial control of robotics
Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

36. Handheld Systems Personal Digital Assistants (PDAs)
Cellular telephones
Issues:
Limited memory
Slow processors
Small display screens.

37. Process Management Activities
The operating system is responsible for the following activities in connection with process management:
Creating and deleting both user and system processes
Suspending and resuming processes
Providing mechanisms for process synchronization
Providing mechanisms for process communication
Providing mechanisms for deadlock handling

38. Open-Source Operating Systems
Operating systems made available in source-code format rather than just binary closed-source
Counter to the copy protection and Digital Rights Management (DRM) movement
Started by Free Software Foundation (FSF), which has “copyleft” GNU Public License (GPL)
Examples include GNU/Linux, BSD UNIX (including core of Mac OS X), and Sun Solaris

39. What makes Operating Systems Exciting and Challenging?

40. Technology Trends: Moore’s Law
Gordon Moore (co-founder of Intel) predicted in 1965 that the transistor density of semiconductor chips would double roughly every 18 months
2X transistors/Chip Every 1.5 years
Called “Moore’s Law”
Moore’s Law
Microprocessors have become smaller, denser, and more powerful

41. New Challenge: Slowdown in Joy’s law of Performance3X
From Hennessy and Patterson, Computer Architecture: A Quantitative Approach, 4th edition, Sept. 15, 2006
 Sea change in chip design: multiple “cores” or processors per chip
VAX : 25%/year 1978 to 1986
RISC + x86 : 52%/year 1986 to 2002
RISC + x86 : ??%/year 2002 to present

42. ManyCore Chips: The future is here
Intel 80-core multicore chip (Feb 2007)
80 simple cores
Two FP-engines / core
Mesh-like network
100 million transistors
65nm feature size
Intel Single-Chip Cloud Computer (August 2010)
24 “tiles” with two cores/tile
24-router mesh network
4 DDR3 memory controllers
Hardware support for message-passing
Amazon X1 instances
128 virtual cores, 2 TB RAM
How to program these?
Use 2 CPUs for video/audio
Use 1 for word processor, 1 for browser
76 for virus checking???
Parallelism must be exploited at all levels

43. Not Only PCs connected to the Internet
Smartphone shipments exceed PC shipments!
2011 shipments:
487M smartphones
414M PC clients
210M notebooks
112M desktops
63M tablets
25M smart TVs
4 billion phones in the world  smartphone over next decade
341.6 million in Q2 2017
61.1 million in Q3 2015
36.2 million in Q1 2017
222 million in 2016

44. Societal Scale Information Systems (Or the “Internet of Things”?)
Clusters
Massive Cluster
Gigabit Ethernet
Societal Scale Information Systems (Or the “Internet of Things”?)
Clusters
Massive Cluster
Gigabit Ethernet
The world is a large distributed system
Microprocessors in everything
Vast infrastructure behind them
Scalable, Reliable,
Secure Services
Internet Connectivity
Databases
Information Collection
Remote Storage
Online Games
Commerce …
Of the enormous variety of CITRIS projects going on at Berkeley, I will present one set that is tied together by this picture: the design, construction and use of MEMS devices, the sensor networks containing them, and making the information from these networks available to widely distributed users as scalable, reliable and secure services.
The name we give to such an integrated system is a Societal Scale Information System, a name meant to evoke its scale – enormous - and purpose – benefiting people and the economy.
I will leave the details of all the specific applications that Ruzena mentioned, be it to energy efficiency or education or disaster response the social sciences, and indeed most details, to later talks and posters.
MEMS for
Sensor Nets