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iv_work(3)                ivykis programmer's manual                iv_work(3)


NAME

       IV_WORK_POOL_INIT, iv_work_pool_create, iv_work_pool_put,
       IV_WORK_ITEM_INIT, iv_work_pool_submit_work - ivykis worker thread
       management


SYNOPSIS

       #include <iv_work.h>

       struct iv_work_pool {
               int             max_threads;
               void            *cookie;
               void            (*thread_start)(void *cookie);
               void            (*thread_stop)(void *cookie);
       };

       struct iv_work_item {
               void            *cookie;
               void            (*work)(void *cookie);
               void            (*completion)(void *cookie);
       };

       void IV_WORK_POOL_INIT(struct iv_work_pool *this);
       int iv_work_pool_create(struct iv_work_pool *this);
       int iv_work_pool_put(struct iv_work_pool *this);
       void IV_WORK_ITEM_INIT(struct iv_work_item *work);
       int iv_work_pool_submit_work(struct iv_work_pool *this, struct
       iv_work_item *work);


DESCRIPTION

       Calling iv_work_pool_create on a struct iv_work_pool object previously
       initialised by IV_WORK_POOL_INIT creates a pool of worker threads that
       can be used to offload CPU intensive tasks to, so as to prevent
       negatively influencing event handling latency in the calling thread,
       and to enable the use of multiple host CPUs for CPU intensive tasks.

       iv_work dynamically adjusts the number of threads in the pool to the
       amount of work there is to do.  The ->max_threads member of struct
       iv_work_pool specifies the maximum number of threads that will be
       created in this pool.

       Calling iv_work_pool_submit_work on a struct iv_work_item object
       previously initialised by IV_WORK_ITEM_INIT submits a work item to a
       pool.  The ->work member of struct iv_work_item specifies the function
       that will be called in one of the worker threads in the pool specified
       by ->this, with ->cookie as its sole argument.  When the work function
       has completed, iv_work will call the ->completion callback to indicate
       this, also with ->cookie as its sole argument, in the thread that
       iv_work_pool_create was called in for this pool object.

       As a special case, calling iv_work_pool_submit_work with a NULL work
       pool pointer will cause the work item to be processed in the local
       thread, from an iv_task(3) callback.

       If the ->thread_start function pointer specified in struct iv_work_pool
       is not NULL, it will be called upon creation of a new worker thread, in
       the context of the created worker thread, with ->cookie as its sole
       argument.  Calls to ->thread_start are not explicitly serialised, which
       should be kept in mind when manipulating state shared between threads
       from within that callback function.

       Similarly, if iv_work decides to terminate a worker thread, for example
       due to inactivity, ->thread_stop will be called in the context of the
       terminating thread, with ->cookie as its sole argument.  Calls to
       ->thread_stop are also not explicitly serialised.

       iv_work_pool_submit_work can only be called from the thread that
       iv_work_pool_create for this pool object was called in.

       There is no way to cancel submitted work items.

       There is no guaranteed order, FIFO or otherwise, between different work
       items submitted to the same worker thread pool.

       When the user has no more work items to submit to the pool, its
       reference to the pool can be dropped by calling iv_work_pool_put.

       If there are still pending or running work items assigned to this pool
       when iv_work_pool_put is called, those work items will not be canceled,
       but will be allowed to run to completion, and their ->completion
       callbacks will be called as usual.  A similar thing holds for the
       ->thread_start and ->thread_stop callbacks -- they can also still be
       called after iv_work_pool_put returns.  Even so, the memory
       corresponding to the struct iv_work_pool can immediately be freed or
       reused by the user upon return of the iv_work_pool_put call.

       Internally, iv_work uses iv_thread(3) for its thread management.


SEE ALSO

       ivykis(3), iv_thread(3)

ivykis                            2010-09-14                        iv_work(3)

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