Multithreading

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Multithreading
By Sergio Romanello
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Multithreading

• Outline
• What is Multithreading?
• Single vs Multithreaded
• Processes
• Example of Multithreading
• Benefits

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Multithreading

• A thread is a way for the program to fork or
  split itself into two or more simultaneously
  running tasks.
• E.g. alot of software that run on modern desktop
  PCs are
• multithreaded.
• Web browser
• One thread to display images or text.
• Another thread retrieves data from the network.
• Word processor
• One thread is for displaying graphics.
• Another thread is for responding to keystrokes
  from the user.
• Thread for performing spelling and grammar
  checking.

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Single vs Multithreaded Processes

• A traditional process has a single thread of
  control.
• If a process has a multiple thread of control, it
  can perform many tasks at a time.
• A thread shares with other threads belonging to
  the same process its code section, data section,
  and other operating system resources.

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Single vs Multithreaded Processes
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Web Browser Example

• Problem/Example
• Web browser accepts client request for webpage,
  image, sounds, and so on.
• A web browser server may have several clients
  concurrently accessing it.
• If the web browser ran as a traditional single
  threaded process, it would be able to service
  only one client at a time. The amount of
• time the client may have to wait is enormous.

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Web Browser Example

• Solution 1
• When a server receives a request, it creates a
  separate process to service that request.
• Old solution before threads become popular.
• Disadvantage
• Time consuming and resource intensive, new
  process will perform the same task as the
  existing process.

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Web Browser Example

• Solution 2
• It is more efficient to use one process with
  multiple threads.
• Multithreaded web server process.
• Create a separate thread that would listen for
  client requests.
• When a request is made, rather than creating
  another process, the server would create another
  thread to serve that request.
• Many operating systems are multithreaded.
• Linux is multithreaded.

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Benefits of Multithreading

• Responsiveness multithreading an interactive
  application may allow a program to continue
  running even if part of it is blocked or
  performing a length operation.
• Resource Sharing the thread share the memory and
  the resources of the process to which they
  belong.
• Economy allocating memory and resources for
  process creation is costly.
• Utilization of Multi Processor Architecture the
  benefits of multithreading can be greatly
  increased in a multiprocessor architecture where
  threads running on parallel on different
  processors.