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Parallel Process Control

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In this project, I have implemented two programs that control the number of worker threads running in parallel. One program uses processes, and the other uses threads.

Overview

  • Read a configuration file to decide how many worker processes or threads should be used.
  • Allow the number of worker processes or threads to be changed at runtime by re-reading the configuration file when necessary (SIGHUP signal for processes, chosen inter-thread communication method for threads).
  • The "work" performed by the workers can be any tasks, function calls. Here, I have used an empty while loop.
  • Worker processes or threads cleans up any resources and print a message before exiting.

Process herder

  • Use signals to communicate with worker processes.
  • Use SIGINT to tell worker processes to cleanly exit.
  • The main process cleans up any resources and waits for all child processes to exit before quitting when it receives a SIGINT signal.

Thread herder

  • Use a chosen inter-thread communication method to control worker threads.
  • The supervisor thread only exits after all worker threads have exited, cleaning up any resources before exiting.

What I have learned

Through this project, I learned how to:

  • Use of fork and signals to communicate with processes, eg. SIGUSR1, SIGHUP, SIGINT.
  • Use inter-thread communication methods to control threads, eg, p_threads.
  • Read and interpret a configuration file while other processes are running.
  • Change the number of worker processes or threads at runtime.
  • Ensure that worker processes or threads clean up resources and exit cleanly.

Managing processes and communication with signals

Processes are independent units of execution within a system. In order to manage processes and communicate in between them, signals can be used.

Signals are a means of communication between processes in a system. They can be used to send a notification or request to another process, or to interrupt the execution of a process.

Managing threads and communication through shared memory

Threads are independent units of execution within a process. In order to manage threads and communicate with them, shared memory can be used.

Shared memory is a region of memory that can be accessed by multiple processes or threads. It allows processes or threads to communicate and share data with each other.

NOTE: running "make" without the quotes will compile all three files with a clean rule.

Compile

on the terminal, to compile,

    make

If you want to just compile 1 file,

    make procs

or

    make threads

NOTE:

  • Config filename has to be "config.txt" without the quotes in the same directory. Which will be used in the program.
  • The Parent Process ID is printed at the top line of the program. Which will be used later. See below.

Running

1. Process herder

To run write ./{filename}.

    ./procs

Changing config: change the value from inside the config file, save it then send hup from another terminal with the parent process id (eg, 16228)

    kill -HUP 16228

2. Thread herder

To run write ./{filename}.

    ./threads

Changing config: change the value from inside the config file, save it then send hup from another terminal with the parent process id (eg, 16228)

    kill -HUP 16228

To clean object files:

    make clean