Class (GI Struct)

GLib-2.0GLibThreadPool

The GLib.ThreadPool struct represents a thread pool.

A thread pool is useful when you wish to asynchronously fork out the execution of work and continue working in your own thread. If that will happen often, the overhead of starting and destroying a thread each time might be too high. In such cases reusing already started threads seems like a good idea. And it indeed is, but implementing this can be tedious and error-prone.

Therefore GLib provides thread pools for your convenience. An added advantage is, that the threads can be shared between the different subsystems of your program, when they are using GLib.

To create a new thread pool, you use GLib.ThreadPool.new. It is destroyed by GLib.ThreadPool.free.

If you want to execute a certain task within a thread pool, use GLib.ThreadPool.push.

To get the current number of running threads you call GLib.ThreadPool.get_num_threads. To get the number of still unprocessed tasks you call GLib.ThreadPool.unprocessed. To control the maximum number of threads for a thread pool, you use GLib.ThreadPool.get_max_threads. and GLib.ThreadPool.set_max_threads.

Finally you can control the number of unused threads, that are kept alive by GLib for future use. The current number can be fetched with GLib.ThreadPool.get_num_unused_threads. The maximum number can be controlled by GLib.ThreadPool.get_max_unused_threads and GLib.ThreadPool.set_max_unused_threads. All currently unused threads can be stopped by calling GLib.ThreadPool.stop_unused_threads.

Index

Constructors

Properties

exclusive: boolean
func: Func
user_data: any
$gtype: GType<ThreadPool>

Methods

  • Frees all resources allocated for pool.

    If immediate is true, no new task is processed for pool. Otherwise pool is not freed before the last task is processed. Note however, that no thread of this pool is interrupted while processing a task. Instead at least all still running threads can finish their tasks before the pool is freed.

    If wait_ is true, this function does not return before all tasks to be processed (dependent on immediate, whether all or only the currently running) are ready. Otherwise this function returns immediately.

    After calling this function pool must not be used anymore.

    Parameters

    • immediate: boolean

      should pool shut down immediately?

    • wait_: boolean

      should the function wait for all tasks to be finished?

    Returns void

  • Returns the maximal number of threads for pool.

    Returns number

    the maximal number of threads

  • Returns the number of threads currently running in pool.

    Returns number

    the number of threads currently running

  • Moves the item to the front of the queue of unprocessed items, so that it will be processed next.

    Parameters

    • Optionaldata: any

      an unprocessed item in the pool

    Returns boolean

    true if the item was found and moved

  • Inserts data into the list of tasks to be executed by pool.

    When the number of currently running threads is lower than the maximal allowed number of threads, a new thread is started (or reused) with the properties given to g_thread_pool_new(). Otherwise, data stays in the queue until a thread in this pool finishes its previous task and processes data.

    error can be null to ignore errors, or non-null to report errors. An error can only occur when a new thread couldn't be created. In that case data is simply appended to the queue of work to do.

    Before version 2.32, this function did not return a success status.

    Parameters

    • Optionaldata: any

      a new task for pool

    Returns boolean

    true on success, false if an error occurred

  • Sets the maximal allowed number of threads for pool. A value of -1 means that the maximal number of threads is unlimited. If pool is an exclusive thread pool, setting the maximal number of threads to -1 is not allowed.

    Setting max_threads to 0 means stopping all work for pool. It is effectively frozen until max_threads is set to a non-zero value again.

    A thread is never terminated while calling func, as supplied by g_thread_pool_new(). Instead the maximal number of threads only has effect for the allocation of new threads in g_thread_pool_push(). A new thread is allocated, whenever the number of currently running threads in pool is smaller than the maximal number.

    error can be null to ignore errors, or non-null to report errors. An error can only occur when a new thread couldn't be created.

    Before version 2.32, this function did not return a success status.

    Parameters

    • max_threads: number

      a new maximal number of threads for pool, or -1 for unlimited

    Returns boolean

    true on success, false if an error occurred

  • Returns the number of tasks still unprocessed in pool.

    Returns number

    the number of unprocessed tasks

  • This function will return the maximum interval that a thread will wait in the thread pool for new tasks before being stopped.

    If this function returns 0, threads waiting in the thread pool for new work are not stopped.

    Returns number

  • This function will set the maximum interval that a thread waiting in the pool for new tasks can be idle for before being stopped. This function is similar to calling g_thread_pool_stop_unused_threads() on a regular timeout, except this is done on a per thread basis.

    By setting interval to 0, idle threads will not be stopped.

    The default value is 15000 (15 seconds).

    Parameters

    • interval: number

      the maximum interval (in milliseconds) a thread can be idle

    Returns void

  • Sets the maximal number of unused threads to max_threads. If max_threads is -1, no limit is imposed on the number of unused threads.

    The default value is 8 since GLib 2.84. Previously the default value was 2.

    Parameters

    • max_threads: number

      maximal number of unused threads

    Returns void

  • Stops all currently unused threads. This does not change the maximal number of unused threads. This function can be used to regularly stop all unused threads e.g. from g_timeout_add().

    Returns void