The document provides a comprehensive overview of distributed operating systems, covering topics such as design goals, inter-process communication, and synchronization methods. It outlines various operating system types, including mainframe, time-sharing, and real-time systems, alongside their features and management functions. Key concepts like process management, memory management, and networking are discussed in the context of their roles within operating systems, supported by specific examples and architectural considerations.

1. DISTRIBUTED
OPERATING SYSTEMS
Sandeep Kumar Poonia
Head Of Dept. CS/IT
B.E., M.Tech., UGC-NET
LM-IAENG, LM-IACSIT,LM-CSTA, LM-AIRCC, LM-SCIEI, AM-UACEE

2. 1 MCS 5.1 DISTRIBUTED OPERATING SYSTEMS
COURSE OUTLINE
BROAD COVERAGE:
 Introduction to distributed computing systems (DCS)
 DCS design goals, Transparencies, Fundamental
issues
 Distributed Coordination
 Process synchronization
 Inter-process communication
 Deadlocks in distributed systems
 Load scheduling and balancing techniques
 Case Study: Amoeba, Mach, Chorus, DCE
PREREQUISITES
 Operating Systems
 Computer Networks
 Database System

3. REFERENCE BOOKS:
 Distributed Operating Systems Concepts and
Design, Pradeep K. Sinha, PHI
 Distributed Operating Systems by Andrew S
Tannebaum, PHI
 Distributed Operating Systems and Algorithm
Analysis by Randy Chow, Pearson Education.

4. INTRODUCTION TO OPERATING
SYSTEM
 What is an Operating System?
 Mainframe Systems
 Desktop Systems
 Multiprocessor Systems
 Distributed Systems
 Clustered System
 Real -Time Systems
 Handheld Systems
 Computing Environments

5. 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.
 Use the computer hardware in an efficient
manner.

6. COMPUTER SYSTEM COMPONENTS
1.Hardware – provides basic computing resources
(CPU, memory, I/O devices).
2.Operating system – controls and coordinates the
use of the hardware among the various
application programs for the various users.
3.Applications programs – define the ways in
which the system resources are used to solve the
computing problems of the users (compilers,
database systems, video games, business
programs).
4.Users (people, machines, other computers).

7. Program Interface
Humans
User Programs
O.S. Interface
O.S.
Hardware Interface/
Privileged Instructions
Disk/Tape/Memory
ABSTRACT VIEW OF SYSTEM COMPONENTS

8. OPERATING SYSTEM DEFINITIONS
 Resource allocator – manages and allocates
resources.
 Control program – controls the execution of user
programs and operations of I/O devices .
 Kernel – the one program running at all times (all
else being application programs).

9. MAINFRAME SYSTEMS
 Reduce setup time by batching similar jobs
 Automatic job sequencing – automatically
transfers control from one job to another.
First rudimentary operating system.
 Resident monitor
 initial control in monitor
 control transfers to job
 when job completes control transfers pack to
monitor

10. MEMORY LAYOUT FOR A SIMPLE BATCH SYSTEM

11. MULTIPROGRAMMED BATCH SYSTEMS
Several jobs are kept in main memory at the same time, and the
CPU is multiplexed among them.

12. OS FEATURES NEEDED FOR
MULTIPROGRAMMING
 I/O routine supplied by the system.
 Memory management – the system must
allocate the memory to several jobs.
 CPU scheduling – the system must choose
among several jobs ready to run.
 Allocation of devices.

13. TIME-SHARING SYSTEMS–INTERACTIVE COMPUTING
 The CPU is multiplexed among several jobs that
are kept in memory and on disk (the CPU is
allocated to a job only if the job is in memory).
 A job swapped in and out of memory to the disk.
 On-line communication between the user and the
system is provided; when the operating system
finishes the execution of one command, it seeks
the next “control statement” from the user’s
keyboard.
 On-line system must be available for users to
access data and code.

14. 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)

15. 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

16. 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

17. SYMMETRIC MULTIPROCESSING ARCHITECTURE

18. 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

19. 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.

20. GENERAL STRUCTURE OF CLIENT-SERVER

21. CLUSTERED SYSTEMS
 Clustering allows two or more systems to share
storage.
 Provides high reliability.
 Asymmetric clustering: one server runs the
application while other servers standby.
 Symmetric clustering: all N hosts are running the
application.

22. 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.

23. 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.

24. HANDHELD SYSTEMS
 Personal Digital Assistants (PDAs)
 Cellular telephones
 Issues:
 Limited memory
 Slow processors
 Small display screens.

25. 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.
OPERATING SYSTEM
OVERVIEW
Storage
Hierarchy
Fast and Expensive
Slow an Cheap

26. COMPUTER-SYSTEM STRUCTURES
 Computer System Operation
 I/O Structure
 Storage Structure
 Storage Hierarchy
 Hardware Protection
 General System Architecture

27. COMPUTER-SYSTEM ARCHITECTURE

28. COMPUTER-SYSTEM OPERATION
 I/O devices and the CPU can execute concurrently.
 Each device controller is in charge of a particular device
type.
 Each device controller has a local buffer.
 CPU moves data from/to main memory to/from local
buffers
 I/O is from the device to local buffer of controller.
 Device controller informs CPU that it has finished its
operation by causing an interrupt.

29. COMMON FUNCTIONS OF 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.

30. I/O STRUCTURE
 After I/O starts, control returns to user program only
upon I/O completion.
 Wait instruction idles the CPU until the next interrupt
 Wait loop (contention for memory access).
 At most one I/O request is outstanding at a time, no
simultaneous I/O processing.
 After I/O starts, control returns to user program
without waiting for I/O completion.
 System call – request to the operating system to allow user
to wait for I/O completion.
 Device-status table contains entry for each I/O device
indicating its type, address, and state.
 Operating system indexes into I/O device table to
determine device status and to modify table entry to
include interrupt.

31. DIRECT MEMORY ACCESS STRUCTURE
 Used for high-speed I/O devices able to transmit
information at close to memory speeds.
 Device controller transfers blocks of data from
buffer storage directly to main memory without
CPU intervention.
 Only one interrupt is generated per block, rather
than the one interrupt per byte.

32. STORAGE STRUCTURE
 Main memory – only large storage media that the
CPU can access directly.
 Secondary storage – extension of main memory
that provides large nonvolatile storage capacity.
 Magnetic disks – rigid metal or glass platters
covered with magnetic recording material
 Disk surface is logically divided into tracks, which
are subdivided into sectors.
 The disk controller determines the logical interaction
between the device and the computer.

33. STORAGE HIERARCHY
 Storage systems organized in hierarchy.
 Speed
 Cost
 Volatility
 Caching – copying information into faster storage
system; main memory can be viewed as a last
cache for secondary storage.

34. STORAGE-DEVICE HIERARCHY

35. CACHING
 Use of high-speed memory to hold recently-
accessed data.
 Requires a cache management policy.
 Caching introduces another level in storage
hierarchy. This requires data that is
simultaneously stored in more than one level to
be consistent.

36. MIGRATION OF A FROM DISK TO
REGISTER

37. OPERATING-SYSTEM STRUCTURES
 System Components
 Operating System Services
 System Calls
 System Programs
 System Structure
 Virtual Machines
 System Design and Implementation
 System Generation

38. COMMON SYSTEM COMPONENTS
 Process Management
 Main Memory Management
 File Management
 I/O System Management
 Secondary Management
 Networking
 Protection System
 Command-Interpreter System

39. PROCESS MANAGEMENT
 A process is a program in execution. A process
needs certain resources, including CPU time,
memory, files, and I/O devices, to accomplish its
task.
 The operating system is responsible for the
following activities in connection with process
management.
 Process creation and deletion.
 process suspension and resumption.
 Provision of mechanisms for:
 process synchronization
 process communication

40. MAIN-MEMORY MANAGEMENT
 Memory is a large array of words or bytes, each
with its own address. It is a repository of quickly
accessible data shared by the CPU and I/O devices.
 Main memory is a volatile storage device. It loses
its contents in the case of system failure.
 The operating system is responsible for the
following activities in connections with memory
management:
 Keep track of which parts of memory are currently
being used and by whom.
 Decide which processes to load when memory space
becomes available.
 Allocate and deallocate memory space as needed.

41. FILE MANAGEMENT
 A file is a collection of related information
defined by its creator. Commonly, files represent
programs (both source and object forms) and
data.
 The operating system is responsible for the
following activities in connections with file
management:
 File creation and deletion.
 Directory creation and deletion.
 Support of primitives for manipulating files and
directories.
 Mapping files onto secondary storage.
 File backup on stable (nonvolatile) storage media.

42. I/O SYSTEM MANAGEMENT
 The I/O system consists of:
 A buffer-caching system
 A general device-driver interface
 Drivers for specific hardware devices

43. SECONDARY-STORAGE MANAGEMENT Since main memory (primary storage) is volatile
and too small to accommodate all data and
programs permanently, the computer system must
provide secondary storage to back up main
memory.
 Most modern computer systems use disks as the
principle on-line storage medium, for both
programs and data.
 The operating system is responsible for the
following activities in connection with disk
management:
 Free space management
 Storage allocation
 Disk scheduling

44. NETWORKING (DISTRIBUTED SYSTEMS)
 A distributed system is a collection processors
that do not share memory or a clock. Each
processor has its own local memory.
 The processors in the system are connected
through a communication network.
 Communication takes place using a protocol.
 A distributed system provides user access to
various system resources.
 Access to a shared resource allows:
 Computation speed-up
 Increased data availability
 Enhanced reliability

45. OPERATING SYSTEM SERVICES
 Program execution – system capability to load a program into
memory and to run it.
 I/O operations – since user programs cannot execute I/O
operations directly, the operating system must provide some
means to perform I/O.
 File-system manipulation – program capability to read, write,
create, and delete files.
 Communications – exchange of information between
processes executing either on the same computer or on
different systems tied together by a network. Implemented
via shared memory or message passing.
 Error detection – ensure correct computing by detecting
errors in the CPU and memory hardware, in I/O devices, or in
user programs.

46. ADDITIONAL OPERATING SYSTEM FUNCTIONS
Additional functions exist not for helping the user,
but rather for ensuring efficient system operations.
•Resource allocation – allocating resources to multiple
users or multiple jobs running at the same time.
•Accounting – keep track of and record which users
use how much and what kinds of computer resources
for account billing or for accumulating usage
statistics.
•Protection – ensuring that all access to system
resources is controlled.

47. SYSTEM DESIGN GOALS
 User goals – operating system should be
convenient to use, easy to learn, reliable, safe,
and fast.
 System goals – operating system should be easy
to design, implement, and maintain, as well as
flexible, reliable, error-free, and efficient.

48. MECHANISMS AND POLICIES
 Mechanisms determine how to do something,
policies decide what will be done.
 The separation of policy from mechanism is a
very important principle, it allows maximum
flexibility if policy decisions are to be changed
later.

49. PROCESSES
 Process Concept
 Process Scheduling
 Operations on Processes
 Cooperating Processes
 Interprocess Communication
 Communication in Client-Server Systems

50. PROCESS CONCEPT
 An operating system executes a variety of
programs:
 Batch system – jobs
 Time-shared systems – user programs or tasks
 Textbook uses the terms job and process almost
interchangeably.
 Process – a program in execution; process
execution must progress in sequential fashion.
 A process includes:
 program counter
 stack
 data section

51. PROCESS STATE
 As a process executes, it changes state
 new: The process is being created.
 running: Instructions are being executed.
 waiting: The process is waiting for some event to
occur.
 ready: The process is waiting to be assigned to a
process.
 terminated: The process has finished execution.

52. DIAGRAM OF PROCESS STATE

53. PROCESS CONTROL BLOCK (PCB)
Information associated with each process.
 Process state
 Program counter
 CPU registers
 CPU scheduling information
 Memory-management information
 Accounting information
 I/O status information

54. PROCESS CONTROL BLOCK (PCB)

55. CPU SWITCH FROM PROCESS TO PROCESS

56. CONTEXT SWITCH
 When CPU switches to another process, the
system must save the state of the old process and
load the saved state for the new process.
 Context-switch time is overhead; the system does
no useful work while switching.
 Time dependent on hardware support.

57. PROCESS CREATION
 Parent process create children processes, which,
in turn create other processes, forming a tree of
processes.
 Resource sharing
 Parent and children share all resources.
 Children share subset of parent’s resources.
 Parent and child share no resources.
 Execution
 Parent and children execute concurrently.
 Parent waits until children terminate.

58. PROCESS TERMINATION
 Process executes last statement and asks the
operating system to decide it (exit).
 Output data from child to parent (via wait).
 Process’ resources are deallocated by operating
system.
 Parent may terminate execution of children
processes (abort).
 Child has exceeded allocated resources.
 Task assigned to child is no longer required.
 Parent is exiting.
 Operating system does not allow child to continue if its
parent terminates.
 Cascading termination.

59. COOPERATING PROCESSES
 Independent process cannot affect or be affected
by the execution of another process.
 Cooperating process can affect or be affected by
the execution of another process
 Advantages of process cooperation
 Information sharing
 Computation speed-up
 Modularity
 Convenience

60. PRODUCER-CONSUMER PROBLEM
 Paradigm for cooperating processes, producer
process produces information that is consumed
by a consumer process.
 unbounded-buffer places no practical limit on the size
of the buffer.
 bounded-buffer assumes that there is a fixed buffer
size.

61. REMOTE PROCEDURE CALLS
 Remote procedure call (RPC) abstracts procedure
calls between processes on networked systems.
 Stubs – client-side proxy for the actual procedure
on the server.
 The client-side stub locates the server and
marshalls the parameters.
 The server-side stub receives this message,
unpacks the marshalled parameters, and peforms
the procedure on the server.

62. REMOTE METHOD INVOCATION
 Remote Method Invocation (RMI) is a Java
mechanism similar to RPCs.
 RMI allows a Java program on one machine to
invoke a method on a remote object.

63. THREADS
 Overview
 Multithreading Models
 Threading Issues
 Windows 2000 Threads
 Linux Threads
 Java Threads

64. SINGLE AND MULTITHREADED PROCESSES

65. BENEFITS
 Responsiveness
 Resource Sharing
 Economy
 Utilization of MP Architectures

66. USER THREADS
 Thread management done by user-level threads
library
 Examples
- POSIX Pthreads
- Mach C-threads
- Solaris threads

67. KERNEL THREADS
 Supported by the Kernel
 Examples
- Windows 95/98/NT/2000
- Solaris
- Tru64 UNIX
- BeOS
- Linux

68. MULTITHREADING MODELS
 Many-to-One
 One-to-One
 Many-to-Many

69. MANY-TO-ONE
 Many user-level threads mapped to single kernel
thread.
 Used on systems that do not support kernel
threads.

70. MANY-TO-ONE MODEL

71. ONE-TO-ONE
 Each user-level thread maps to kernel thread.
 Examples
- Windows 95/98/NT/2000
- OS/2

72. ONE-TO-ONE MODEL

73. MANY-TO-MANY MODEL
 Allows many user level threads to be mapped to
many kernel threads.
 Allows the operating system to create a
sufficient number of kernel threads.
 Solaris 2
 Windows NT/2000 with the ThreadFiber package

74. MANY-TO-MANY MODEL

75. WINDOWS 2000 THREADS
 Implements the one-to-one mapping.
 Each thread contains
- a thread id
- register set
- separate user and kernel stacks
- private data storage area

76. LINUX THREADS
 Linux refers to them as tasks rather than
threads.
 Thread creation is done through clone() system
call.
 Clone() allows a child task to share the address
space of the parent task (process)

77. JAVA THREADS
 Java threads may be created by:
 Extending Thread class
 Implementing the Runnable interface
 Java threads are managed by the JVM.