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Department of Computer Science Southern Illinois University Edwardsville Spring, 2010

Inter-Process Communication (IPC). CS 547/490 Network Programming. Department of Computer Science Southern Illinois University Edwardsville Spring, 2010 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu. IPC1.PPT/001. Address Space for A. IPC. Process A. Process B. Computer.

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Department of Computer Science Southern Illinois University Edwardsville Spring, 2010

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  1. Inter-Process Communication (IPC) CS 547/490 Network Programming Department of Computer Science Southern Illinois University Edwardsville Spring, 2010 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu IPC1.PPT/001

  2. Address Space for A IPC Process A Process B Computer Address Space for B CS 547/490 Network Programming Inter Process Communication: What is “IPC”? IPC is a mechanism for two processes to communicate IPC1.PPT/002

  3. CS 547/490 Network Programming Five Methods for IPC: 1. Pipes (Named Pipes) 2. Message Queue 3. Shared memory 4. Semaphore 5. Monitor IPC1.PPT/003

  4. We can use it through “system calls” CS 547/490 Network Programming What is “pipe”? A pipe is essentially a FIFO data structure (queue) created by OS. Pipe is a shared memory (or shared file) A pipe provides a unidirectional communication channel. A pipe is a communication channel through OS. A pipe provides a communication channel between two independent processes. IPC1.PPT/004

  5. Concept of pipe visualized Process 1 Process 2  Between two processes  Pipe is a FIFO queue FIFO Queue  Pipe is created by OS CS 547/490 Network Programming  Unidirectional channel IPC1.PPT/005

  6.   Process 1 Process 2       CS 547/490 Network Programming • Detailed work is taken care of by OS - The order is preserved by OS - Race condition will not happen FIFO Queue - FIFO enforced by OS (Abstraction of “queue”) IPC1.PPT/006

  7. CS 547/490 Network Programming Five application models for pipe 1. Single Process Model 2. Parallel Multi-Process Model 3. Sequential Multi-Process Model 4. Chain Multi-Process Model 5.Circular Multi-Process Model: IPC1.PPT/007

  8. Process read (pd); pd = pipe; write (pd); FIFO Queue OS CS 547/490 Network Programming (1) Single-Process Model: • External FIFO buffer • Indirect access to FIFO IPC1.PPT/008

  9. FIFO Queue FIFO Queue (Pipe) CS 547/490 Network Programming (1) Single-Process Model (continued): Process read (FIFO); • Internal FIFO buffer • Direct access to FIFO write (FIFO); OS IPC1.PPT/009

  10. Application Example File Request Thread 1 Thread 2 write (fd); read (fd); DISK FIFO Queue CS 547/490 Network Programming (1) Single-Process Model (continued): File Server OS IPC1.PPT/010

  11. Disadvantages Advantages CS 547/490 Network Programming (1) Single-Process Model (continued): • OS takes care of “race condition” problem (some operating systems) • High level of abstraction - Operations as system calls - “Create FIFO”, “Delete FIFO”, “Remove an element”, … etc. - “Fail-safe”: data will be in pipe even after a user process crashes • High overhead (each operation requires system call) • Program becomes “OS dependent” - Can not run on an OS which does not support pipe. IPC1.PPT/011

  12. Process 1 Process 2 read (pd); read (pd); folk write (pd); write (pd); FIFO Queue (Pipe) CS 547/490 Network Programming (2) Parallel Multi-Process Model: OS IPC1.PPT/012

  13. General Parallel Multi-Process Model Process 1 Process 2 Process n    Pipe CS 547/490 Network Programming (2) Parallel Multi-Process Model (continued): IPC1.PPT/013

  14. Application Example  When a request arrives, put the request in the pipe. Server 1  Remove the first job from the pipe. Disk Pipe Server 2 Disk Server n Disk CS 547/490 Network Programming (2) Parallel Multi-Process Model (continued):  Transmit the requested file IPC1.PPT/014

  15. Process 1 Process 1’ read (pd); read (pd); folk write (pd); write (pd); close close CS 547/490 Network Programming (3) Sequential Multi-Process Model: FIFO Queue (Pipe) OS IPC1.PPT/016

  16. Process 1 Process 1’ read (pd); read (pd); write (pd); write (pd); CS 547/490 Network Programming (3) Sequential Multi-Process Model (continued): FIFO Queue (Pipe) OS IPC1.PPT/017

  17. Application Example Transmit Requested File Incoming Request Authenticator File Server read (pd); write (pd); DISK FIFO Queue (Pipe) CS 547/490 Network Programming (3) Sequential Multi-Process Model (continued): OS IPC1.PPT/018

  18. Application Example Server 1 Disk Server 2 Pipe Disk CS 547/490 Network Programming (3) Sequential Multi-Process Model (continued): Authorizer 1 Authorizer 2       Authorizer n Server n Disk IPC1.PPT/019

  19. DISK J6 J5 J4 J3 J2 FIFO File Server Disadvantages Advantages Small jobs stack after a big one CS 547/490 Network Programming (3) Sequential Multi-Process Model (continued): • Better response time - “convoy effect” J1 • High running cost - Hardware/Software Cost - Maintenance Cost - Disk Mirroring IPC1.PPT/020

  20. Pipe 1 Pipe 2 Process 1 Process 2 Process 3 CS 547/490 Network Programming (4) Chain Multi-Process Model: IPC1.PPT/021

  21. Application Example CS 547/490 Network Programming (4) Chain Multi-Process Model (continued): Possible applications? 1. Compiler, assembler, Linker 2. Any processes that contain “steps” 3. Multimedia Stream Decorder/Encorder (File access, encoding, file transmission, etc) IPC1.PPT/022

  22. Process 1 Process 2 read (pd); read (pd); write (pd); write (pd); CS 547/490 Network Programming (5) Circular Multi-Process Model: OS IPC1.PPT/023

  23. Application Example Pipe 2 Client 1 Client 2 Client n Server Pipe 1 CS 547/490 Network Programming (5) Circular Multi-Process Model (continued): Computer IPC1.PPT/024

  24. Disadvantages Advantages CS 547/490 Network Programming (5) Circular Multi-Process Model (continued): • Better security - Users (requestors) can not directly access server • Flexibility (Modularity) - Server can be modified (upgraded) without changing client • High cost (hardware) • Pipe may be a performance bottleneck IPC1.PPT/025

  25. Application Example Server 2 Server 1 Server n Disk Disk Disk Pipe CS 547/490 Network Programming (2) Parallel Multi-Process Model (continued): Job Dispatcher IPC_1.PPT/001

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