Method prepare_task_pool

benchmarks/tbb/scheduler.cpp:425–463

}

size_t generic_scheduler::prepare_task_pool ( size_t num_tasks ) {
    size_t T = __TBB_load_relaxed(my_arena_slot->tail); // mirror
    if ( T + num_tasks <= my_arena_slot->my_task_pool_size )
        return T;
    acquire_task_pool();
    size_t H = __TBB_load_relaxed(my_arena_slot->head); // mirror
    T -= H;
    size_t new_size = T + num_tasks;
    __TBB_ASSERT(!my_arena_slot->my_task_pool_size || my_arena_slot->my_task_pool_size >= min_task_pool_size, NULL);
    if( !my_arena_slot->my_task_pool_size ) {
        __TBB_ASSERT( !in_arena() && !my_arena_slot->task_pool_ptr, NULL );
        if( new_size < min_task_pool_size ) new_size = min_task_pool_size;
        my_arena_slot->allocate_task_pool( new_size );
    }
    // If the free space at the beginning of the task pool is too short, we
    // are likely facing a pathological single-producer-multiple-consumers
    // scenario, and thus it's better to expand the task pool
    else if ( new_size <= my_arena_slot->my_task_pool_size - min_task_pool_size/4 ) {
        // Relocate the busy part to the beginning of the deque
        memmove( my_arena_slot->task_pool_ptr, my_arena_slot->task_pool_ptr + H, T * sizeof(task*) );
        my_arena_slot->fill_with_canary_pattern( T, my_arena_slot->tail );
        commit_relocated_tasks(T);
    }
    else {
        // Grow task pool. As this operation is rare, and its cost is asymptotically
        // amortizable, we can tolerate new task pool allocation done under the lock.
        if ( new_size < 2 * my_arena_slot->my_task_pool_size )
            new_size = 2 * my_arena_slot->my_task_pool_size;
        task** old_pool = my_arena_slot->task_pool_ptr;
        my_arena_slot->allocate_task_pool( new_size ); // updates my_task_pool_size
        __TBB_ASSERT( T <= my_arena_slot->my_task_pool_size, "new task pool is too short" );
        memcpy( my_arena_slot->task_pool_ptr, old_pool + H, T * sizeof(task*) );
        commit_relocated_tasks(T);
        __TBB_ASSERT( old_pool, "attempt to free NULL TaskPool" );
        NFS_Free( old_pool );
    }
    assert_task_pool_valid();
    return T;
}

/** ATTENTION:
    This method is mostly the same as generic_scheduler::lock_task_pool(), with