1. Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne ©2007 Chapter 3: Processes

2. 3.2 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Chapter 3: Processes  What is a process?  How are procs scheduled?  What are allowable operations on procs?  How do procs cooperate or conflict?  How do procs communicate with each other?

3. 3.3 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Concept  Process – a program in execution  Process Control Block (PCB) for each proc CPU registers and program counter Stack Static data CPU scheduling info Memory-management info Accounting info I/O status info Process state

4. 3.4 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Control Block (PCB)

5. 3.5 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process in Memory

6. 3.6 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 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  Kernel service like i/o or authentication ready: The process is waiting its turn to run terminated: The process has finished execution

7. 3.7 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 State Transition Diagram for Procs, ver. 1 Page 87, Fig. 3.2

8. 3.8 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 CPU Switch From Process to Process Page 89, Fig. 3.4

9. 3.9 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Scheduling Queues  Job queue – set of all procs in the system  Ready queue – set of all procs waiting to execute  Device queues – set of procs waiting for an I/O device  Processes migrate among the various queues

10. 3.10 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Ready Queue And Various I/O Device Queues

11. 3.11 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Schedulers  Long-term scheduler (or job scheduler) Which procs should be brought into the ready queue?  Short-term scheduler (or CPU scheduler) Which proc should be executed next and on which CPU? Long-term scheduler Short-term scheduler

12. 3.12 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Representation of Process Scheduling

13. 3.13 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Medium Term Scheduler (Swapper)

14. 3.14 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Schedulers (Cont.)  Short-term scheduler is invoked frequently (millisecs)  (fast)  Long-term scheduler is invoked infrequently (secs, mins)  (slow)  Long-term scheduler controls “degree of multiprogramming”  Procs are either I/O-bound – more time in I/O than computing; many, short CPU bursts CPU-bound – more time computing than I/O; few, long CPU bursts

15. 3.15 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Context Switch  Kernel CPU time to switch to another proc: Save state of old proc, load saved state of new proc  Context-switch is overhead, not useful work  Modern CPUs have hardware support E.g. Sun SPARC register window http://www.extremetech.com/article2/0,1697,1158259,00.asp

16. 3.16 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Creation  Parent procs create children, forming a tree of procs  Resource sharing: some, all, or none  Execution: concurrently or parent wait  Address space: duplicate or separate  UNIX system call example: fork creates new proc exec after a fork replaces proc’s memory with a new program

17. 3.17 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Creation in POSIX Page 97, Fig. 3.10

18. 3.18 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Creation in Win32

19. 3.19 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Creation in Java

20. 3.20 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Process Termination  Process executes last statement and asks the operating system to delete 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 If parent is exiting  Some operating system do not allow child to continue if its parent terminates  All children terminated - cascading termination

21. Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne ©2007 End of Day 8 Lecture Read to p. 116 in Chapter 3 Come to Frey 366 Lab

22. 3.22 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Reminders (Day 10)  Show ProcessExplorer on Windows.  Quiz: Give an example for each of these three things: 1. A file system that always uses a B-tree. 2. A file system that has always been stateful. 3. A file system that supports journaling.

23. 3.23 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Interprocess Communication Message PassingShared Memory

24. 3.24 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Producer-Consumer Problem  Paradigm for cooperating processes, producer proc produces information that is consumed by a consumer proc unbounded-buffer -- no practical limit on size of buffer bounded-buffer -- fixed buffer size

25. 3.25 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Sharing Memory in Java

26. 3.26 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer: Shared-Memory Solution Page 102, Fig. 3.15

27. 3.27 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer: Shared-Memory Solution (cont.) Page 104, Fig. 3.18

28. 3.28 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer: insert() method Page 103, Fig. 3.16

29. 3.29 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer: remove() method Page 103, Fig. 3.17

30. 3.30 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Message Passing: General  Procs communicate without shared variables  Operations: send (message) – message size fixed or variable receive (message)  P and Q communicate, establishing a link, exchanging messages via send/receive  Implementation of link physical (e.g., shared memory, hardware bus) logical (e.g., queue)

31. 3.31 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Message Passing Implementation  How are links established?  Can a link be associated with more than two processes?  How many links can there be between every pair of communicating processes?  What is the capacity of a link?  Is the size of a message that the link can accommodate fixed or variable?  Is a link unidirectional or bi-directional?

32. 3.32 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Strategy #1: Direct Communication  Processes name each other explicitly: send (P, message) – send message to proc P receive (Q, message) – receive message from proc Q  Links established automatically  Link associated with one pair of procs  Between each pair there exists exactly one link  Link is unidirectional, or more commonly bi-directional

33. 3.33 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Strategy #2: Indirect Communication  Messages through queues called mailboxes or ports ( ls | more or FTP on port 21) Each mailbox has a unique id Procs communicate by sharing mailbox  Properties of mailboxes May be associated with many procs Procs may share many mailboxes Mailboxes be unidirectional or bi-directional

34. 3.34 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Indirect Communication (cont.)  Operations create a new mailbox destroy a mailbox send and receive send(A, message) – send a message to mailbox A receive(A, message) – receive a message from mailbox A

35. 3.35 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Indirect Communication (cont.)  Mailbox sharing P 1, P 2, and P 3 share mailbox A P 1, sends; P 2 and P 3 receive Who gets the message?  Solutions Allow a link to be associated with at most two procs Allow only one proc at a time to execute a receive operation Allow OS to select arbitrary receiver. Sender is notified who receiver was.

36. 3.36 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Synchronization of message passing  Blocking is synchronous Blocking send has the sender block until the message is received Blocking receive has the receiver block until a message is available  Non-blocking is asynchronous Non-blocking send has the sender send the message and continue Non-blocking receive has the receiver receive a valid message or null

37. 3.37 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Buffer capacity  Queue of messages attached to the link: either 1.Zero capacity – 0 messages. Sender must wait for receiver (“rendezvous”). 2.Bounded capacity – n messages. Sender must wait if link full. 3.Unbounded capacity – infinite length Sender never waits.

38. 3.38 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer: Message Passing Solution Page 109, Fig. 3.20

39. 3.39 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer – Message Passing Solution Page 109, Fig. 3.21

40. 3.40 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer – Message Passing Solution The Producer Page 110, Fig. 3.22

41. 3.41 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Bounded-Buffer – Message Passing Solution The Consumer Page 110, Fig. 3.23

42. 3.42 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 LPC Message Passing, WinXP, 3 ways Page 113, Fig. 3.24

43. 3.43 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Client-Server Communication  Sockets (TCP/IP or UDP/IP on any port)  RPC (Remote Procedure Calls)  RMI (Remote Method Invocation, Java)

44. 3.44 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Sockets  A socket is an endpoint for communication  The socket 146.86.5.20:1625 refers to port 1625 on host 146.86.5.20 Page 114, Fig. 3.25

45. 3.45 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Socket Communication in Java Page 115, Fig. 3.26

46. 3.46 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Socket Communication in Java (cont.) Page 116, Fig. 3.27

47. Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne ©2007 End of Day 10 lecture Finish reading Chapter 3

48. 3.48 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Remote Procedure Calls (RPC)  Abstracts calls between procs across networks.  Stubs – client-side proxy for the remote proc.  The stub locates the server (the “matchmaker daemon”) and marshalls the parameters.  Server-side receives this message, unpacks the marshalled parameters, performs the proc, and returns a value to the client.

49. 3.49 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Execution of Remote Procedure Call Page 119, Fig. 3.28

50. 3.50 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Remote Method Invocation (RMI)  A Java mechanism similar to RPCs:  A program on one machine invokes a method on a remote object, including passing object parameters that implement java.io.Serializable

51. 3.51 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Marshalling Parameters

52. 3.52 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 RMI Example

53. 3.53 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 RMI Example

54. 3.54 Silberschatz, Galvin and Gagne ©2007 Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 RMI Example

55. Operating System Concepts with Java – 7 th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne ©2007 End of Chapter 3