/* * This file is part of the StarPU Handbook. * Copyright (C) 2009--2011 Universit@'e de Bordeaux * Copyright (C) 2010, 2011, 2012, 2013, 2014, 2016, 2017 CNRS * Copyright (C) 2011, 2012 INRIA * See the file version.doxy for copying conditions. */ /*! \defgroup API_Scheduling_Policy Scheduling Policy \brief TODO. While StarPU comes with a variety of scheduling policies (see \ref TaskSchedulingPolicy), it may sometimes be desirable to implement custom policies to address specific problems. The API described below allows users to write their own scheduling policy. \def STARPU_MAXIMPLEMENTATIONS \ingroup API_Scheduling_Policy Define the maximum number of implementations per architecture. The default value can be modified at configure by using the option \ref enable-maximplementations "--enable-maximplementations". \struct starpu_sched_policy \ingroup API_Scheduling_Policy Contain all the methods that implement a scheduling policy. An application may specify which scheduling strategy in the field starpu_conf::sched_policy passed to the function starpu_init(). For each task going through the scheduler, the following methods get called in the given order: For each task not going through the scheduler (because starpu_task::execute_on_a_specific_worker was set), these get called: \var void (*starpu_sched_policy::init_sched)(unsigned sched_ctx_id) Initialize the scheduling policy, called before any other method. \var void (*starpu_sched_policy::deinit_sched)(unsigned sched_ctx_id) Cleanup the scheduling policy, called before any other method. \var int (*starpu_sched_policy::push_task)(struct starpu_task *) Insert a task into the scheduler, called when the task becomes ready for execution. \var void (*starpu_sched_policy::push_task_notify)(struct starpu_task *, int workerid, int perf_workerid, unsigned sched_ctx_id) Notify the scheduler that a task was pushed on a given worker. This method is called when a task that was explicitly assigned to a worker becomes ready and is about to be executed by the worker. This method therefore permits to keep the state of the scheduler coherent even when StarPU bypasses the scheduling strategy. \var struct starpu_task *(*starpu_sched_policy::pop_task)(unsigned sched_ctx_id) Get a task from the scheduler. If this method returns NULL, the worker will start sleeping. If later on some task are pushed for this worker, starpu_wake_worker() must be called to wake the worker so it can call the pop_task() method again. The mutex associated to the worker is already taken when this method is called. This method may release it (e.g. for scalability reasons when doing work stealing), but it must acquire it again before taking the decision whether to return a task or NULL, so the atomicity of deciding to return NULL and making the worker actually sleep is preserved. Otherwise in simgrid or blocking driver mode the worker might start sleeping while a task has just been pushed for it. If this method is defined as NULL, the worker will only execute tasks from its local queue. In this case, the push_task method should use the starpu_push_local_task method to assign tasks to the different workers. \var struct starpu_task *(*starpu_sched_policy::pop_every_task)(unsigned sched_ctx_id) Remove all available tasks from the scheduler (tasks are chained by the means of the field starpu_task::prev and starpu_task::next). The mutex associated to the worker is already taken when this method is called. This is currently not used and can be discarded. \var void (*starpu_sched_policy::submit_hook)(struct starpu_task *) Optional field. This method is called when a task is submitted. \var void (*starpu_sched_policy::pre_exec_hook)(struct starpu_task *) Optional field. This method is called every time a task is starting. \var void (*starpu_sched_policy::post_exec_hook)(struct starpu_task *) Optional field. This method is called every time a task has been executed. \var void (*starpu_sched_policy::do_schedule)(unsigned sched_ctx_id) Optional field. This method is called when it is a good time to start scheduling tasks. This is notably called when the application calls starpu_task_wait_for_all or starpu_do_schedule explicitly. \var void (*starpu_sched_policy::add_workers)(unsigned sched_ctx_id, int *workerids, unsigned nworkers) Initialize scheduling structures corresponding to each worker used by the policy. \var void (*starpu_sched_policy::remove_workers)(unsigned sched_ctx_id, int *workerids, unsigned nworkers) Deinitialize scheduling structures corresponding to each worker used by the policy. \var const char *starpu_sched_policy::policy_name Optional field. Name of the policy. \var const char *starpu_sched_policy::policy_description Optional field. Human readable description of the policy. \fn struct starpu_sched_policy **starpu_sched_get_predefined_policies() \ingroup API_Scheduling_Policy Return an NULL-terminated array of all the predefined scheduling policies. \fn void starpu_worker_get_sched_condition(int workerid, starpu_pthread_mutex_t **sched_mutex, starpu_pthread_cond_t **sched_cond) \ingroup API_Scheduling_Policy When there is no available task for a worker, StarPU blocks this worker on a condition variable. This function specifies which condition variable (and the associated mutex) should be used to block (and to wake up) a worker. Note that multiple workers may use the same condition variable. For instance, in the case of a scheduling strategy with a single task queue, the same condition variable would be used to block and wake up all workers. \fn int starpu_wake_worker_no_relax(int workerid) \ingroup API_Scheduling_Policy Must be called to wake up a worker that is sleeping on the cond. Return 0 whenever the worker is not in a sleeping state or has the state_keep_awake flag on. \fn int starpu_wake_worker_locked(int workerid) \ingroup API_Scheduling_Policy Version of starpu_wake_worker_no_relax() which assumes that the sched mutex is locked \fn int starpu_sched_set_min_priority(int min_prio) \ingroup API_Scheduling_Policy TODO: check if this is correct Define the minimum task priority level supported by the scheduling policy. The default minimum priority level is the same as the default priority level which is 0 by convention. The application may access that value by calling the function starpu_sched_get_min_priority(). This function should only be called from the initialization method of the scheduling policy, and should not be used directly from the application. \fn int starpu_sched_set_max_priority(int max_prio) \ingroup API_Scheduling_Policy TODO: check if this is correct Define the maximum priority level supported by the scheduling policy. The default maximum priority level is 1. The application may access that value by calling the function starpu_sched_get_max_priority(). This function should only be called from the initialization method of the scheduling policy, and should not be used directly from the application. \fn int starpu_sched_get_min_priority(void) \ingroup API_Scheduling_Policy TODO: check if this is correct Return the current minimum priority level supported by the scheduling policy \fn int starpu_sched_get_max_priority(void) \ingroup API_Scheduling_Policy TODO: check if this is correct Return the current maximum priority level supported by the scheduling policy \fn int starpu_push_local_task(int workerid, struct starpu_task *task, int back) \ingroup API_Scheduling_Policy The scheduling policy may put tasks directly into a worker’s local queue so that it is not always necessary to create its own queue when the local queue is sufficient. If \p back is not 0, \p task is put at the back of the queue where the worker will pop tasks first. Setting \p back to 0 therefore ensures a FIFO ordering. \fn int starpu_push_task_end(struct starpu_task *task) \ingroup API_Scheduling_Policy Must be called by a scheduler to notify that the given task has just been pushed. \fn int starpu_worker_can_execute_task(unsigned workerid, struct starpu_task *task, unsigned nimpl) \ingroup API_Scheduling_Policy Check if the worker specified by workerid can execute the codelet. Schedulers need to call it before assigning a task to a worker, otherwise the task may fail to execute. \fn int starpu_worker_can_execute_task_impl(unsigned workerid, struct starpu_task *task, unsigned *impl_mask) \ingroup API_Scheduling_Policy Check if the worker specified by workerid can execute the codelet and returns which implementation numbers can be used. Schedulers need to call it before assigning a task to a worker, otherwise the task may fail to execute. This should be preferred rather than calling starpu_worker_can_execute_task for each and every implementation. It can also be used with impl_mask == NULL to check for at least one implementation without determining which. \fn int starpu_worker_can_execute_task_first_impl(unsigned workerid, struct starpu_task *task, unsigned *nimpl) \ingroup API_Scheduling_Policy Check if the worker specified by workerid can execute the codelet and returns the first implementation which can be used. Schedulers need to call it before assigning a task to a worker, otherwise the task may fail to execute. This should be preferred rather than calling starpu_worker_can_execute_task for each and every implementation. It can also be used with impl_mask == NULL to check for at least one implementation without determining which. \fn uint32_t starpu_task_footprint(struct starpu_perfmodel *model, struct starpu_task *task, struct starpu_perfmodel_arch *arch, unsigned nimpl) \ingroup API_Scheduling_Policy Return the footprint for a given task, taking into account user-provided perfmodel footprint or size_base functions. \fn uint32_t starpu_task_data_footprint(struct starpu_task *task) \ingroup API_Scheduling_Policy Return the raw footprint for the data of a given task (without taking into account user-provided functions). \fn double starpu_task_expected_length(struct starpu_task *task, struct starpu_perfmodel_arch *arch, unsigned nimpl) \ingroup API_Scheduling_Policy Return expected task duration in micro-seconds. \fn double starpu_worker_get_relative_speedup(struct starpu_perfmodel_arch *perf_arch) \ingroup API_Scheduling_Policy Return an estimated speedup factor relative to CPU speed \fn double starpu_task_expected_data_transfer_time(unsigned memory_node, struct starpu_task *task) \ingroup API_Scheduling_Policy Return expected data transfer time in micro-seconds. \fn double starpu_data_expected_transfer_time(starpu_data_handle_t handle, unsigned memory_node, enum starpu_data_access_mode mode) \ingroup API_Scheduling_Policy Predict the transfer time (in micro-seconds) to move \p handle to a memory node \fn double starpu_task_expected_energy(struct starpu_task *task, struct starpu_perfmodel_arch *arch, unsigned nimpl) \ingroup API_Scheduling_Policy Return expected energy consumption in J \fn double starpu_task_expected_conversion_time(struct starpu_task *task, struct starpu_perfmodel_arch *arch, unsigned nimpl) \ingroup API_Scheduling_Policy Return expected conversion time in ms (multiformat interface only) \fn int starpu_get_prefetch_flag(void) \ingroup API_Scheduling_Policy Whether \ref STARPU_PREFETCH was set \fn int starpu_prefetch_task_input_on_node(struct starpu_task *task, unsigned node) \ingroup API_Scheduling_Policy Prefetch data for a given task on a given node \fn int starpu_idle_prefetch_task_input_on_node(struct starpu_task *task, unsigned node) \ingroup API_Scheduling_Policy Prefetch data for a given task on a given node when the bus is idle \fn void starpu_sched_ctx_worker_shares_tasks_lists(int workerid, int sched_ctx_id) \ingroup API_Scheduling_Policy The scheduling policies indicates if the worker may pop tasks from the list of other workers or if there is a central list with task for all the workers */