Multithreading and Thread Libraries: An In-depth Look, Slides of Operating Systems

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Lecture 7

Chapter 4: Threads (cont)

Chapter 4: Threads

• Overview
• Multithreading Models
• Thread Libraries
• Threading Issues
• Operating System Examples
• Windows XP Threads
• Linux Threads

ex: Solaris, Mach, Windows

ex: MS-DOS ex: Java VM ex: early UNIX

uniprogramming

multiprogramming

Process-Thread relationship

Single and Multithreaded Processes

Benefits

• Responsiveness : Continue even if part of an application is blocked due to I/O - Allow user interaction in one thread while image is loading in another.
• Resource Sharing : Memory / resource sharing is by default with threads. - Several different threads of activity within the same address space.
• Economy : It is more economical to create andDocsity.com

Multicore Scalability

Parallel Execution on a Multicore System

Concurrent Execution on a Single-core System

User Threads

• Thread management done by user-level threads library
• Three primary thread libraries:
  • POSIX Pthreads
  • Win32 threads
  • Java threads

Kernel Threads

• Supported by the Kernel
• Examples
  • Windows XP/
  • Solaris
  • Linux
  • Tru64 UNIX
  • Mac OS X

Many-to-One

• Many user-level threads mapped to single kernel thread.
• Thread management is done by the thread library in user space, - Is efficient, - But, entire process will block is a thread makes a blocking system call.
• Only one thread can access the kernel at a time, Docsity.com

One-to-One

• Each user-level thread maps to kernel thread.
• Provides more concurrency.
  • No blocking due to another thread.
  • Threads may run in parallel on multiprocessors.
• Creating a user thread requires creating the corresponding kernel thread. - Hence, OSes limit the number of threads.

Two-level Model

• Similar to many-to-many, except that it allows a user thread to be bound to kernel thread.
• Examples
  • IRIX
  • HP-UX
  • Tru64 UNIX
  • Solaris 8 and earlier

Pthreads

• May be provided either as user-level or kernel-level
• A POSIX standard (IEEE 1003.1c) API for thread creation and synchronization
• API specifies behavior of the thread library, implementation is up to development of the library

Java Threads

• Java threads are managed by the JVM
• Typically implemented using the threads model provided by underlying OS
• Java threads may be created by:
  • Extending Thread class
  • Implementing the Runnable interface
    • Must define run() method
    • Call start() method to initialize a thread
    • Use join() method to wait for a thread Docsity.com