Ejemplo n.º 1
0
void thorium_worker_pool_assign_worker_to_actor(struct thorium_worker_pool *pool, int name)
{
    int worker_index;

#ifdef THORIUM_WORKER_POOL_USE_LEAST_BUSY
    int score;
#endif

#ifdef THORIUM_WORKER_POOL_USE_SCRIPT_ROUND_ROBIN
    int script;
    struct thorium_actor *actor;
#endif

                /*
    printf("DEBUG Needs to do actor placement\n");
    */
    /* assign this actor to the least busy actor
     */

    worker_index = -1;

#ifdef THORIUM_WORKER_POOL_USE_LEAST_BUSY
    worker_index = thorium_balancer_select_worker_least_busy(&pool->scheduler, &score);

#elif defined(THORIUM_WORKER_POOL_USE_SCRIPT_ROUND_ROBIN)
    actor = thorium_node_get_actor_from_name(pool->node, name);

    /*
     * Somehow this actor dead a while ago.
     */
    if (actor == NULL) {
        return;
    }

    /* The actor can't be dead if it does not have an initial
     * placement...
     */
    CORE_DEBUGGER_ASSERT(actor != NULL);

    script = thorium_actor_script(actor);

    worker_index = thorium_balancer_select_worker_script_round_robin(&pool->balancer, script);
#endif

    CORE_DEBUGGER_ASSERT(worker_index >= 0);

#ifdef THORIUM_WORKER_POOL_DEBUG
    printf("ASSIGNING %d to %d\n", name, worker_index);
#endif

    thorium_balancer_set_actor_worker(&pool->balancer, name, worker_index);
}
Ejemplo n.º 2
0
void biosal_input_controller_prepare_spawners(struct thorium_actor *actor, struct thorium_message *message)
{
    int spawner;
    struct biosal_input_controller *concrete_actor;

    concrete_actor = (struct biosal_input_controller *)thorium_actor_concrete_actor(actor);

#ifdef BIOSAL_INPUT_CONTROLLER_DEBUG
    printf("DEBUG biosal_input_controller_prepare_spawners \n");
#endif

    /* spawn an actor of the same script on every spawner to load required
     * scripts on all nodes
     */
    if (core_queue_dequeue(&concrete_actor->unprepared_spawners, &spawner)) {

        thorium_actor_send_int(actor, spawner, ACTION_SPAWN, thorium_actor_script(actor));
        concrete_actor->state = BIOSAL_INPUT_CONTROLLER_STATE_PREPARE_SPAWNERS;
    }
}
Ejemplo n.º 3
0
Archivo: frame.c Proyecto: huyba/biosal
void frame_receive(struct thorium_actor *actor, struct thorium_message *message)
{
    int tag;
    int name;
    void *buffer;
    struct frame *concrete_actor;
    int other;
    struct core_vector initial_actors;
    struct core_vector *acquaintance_vector;
    int source;

    source = thorium_message_source(message);
    concrete_actor = (struct frame *)thorium_actor_concrete_actor(actor);
    tag = thorium_message_action(message);
    name = thorium_actor_name(actor);
    buffer = thorium_message_buffer(message);
    acquaintance_vector = &concrete_actor->acquaintance_vector;


    if (tag == ACTION_START) {

        core_vector_init(&initial_actors, sizeof(int));
        core_vector_unpack(&initial_actors, buffer);
        core_vector_push_back_vector(acquaintance_vector, &initial_actors);
        core_vector_destroy(&initial_actors);

        other = thorium_actor_spawn(actor, thorium_actor_script(actor));
        core_vector_push_back_int(acquaintance_vector, other);

        thorium_actor_send_empty(actor, other, ACTION_PING);

        printf("actor %d sends ACTION_PING to new actor %d\n",
                        name, other);

    } else if (tag == ACTION_PING) {

        /* new acquaintance
         */
        core_vector_push_back(acquaintance_vector, &source);

        printf("actor %d (value %d) receives ACTION_PING from actor %d\n",
                        name, concrete_actor->value, source);
        printf("Acquaintances of actor %d: ", name);
        core_vector_print_int(acquaintance_vector);
        printf("\n");

        thorium_actor_send_reply_empty(actor, ACTION_PING_REPLY);

    } else if (tag == ACTION_PING_REPLY) {

        concrete_actor->pings++;

        printf("actor %d receives ACTION_PING_REPLY from actor %d\n",
                        name, source);

        /* kill the system
         */
        if (concrete_actor->migrated_other && concrete_actor->pings == 2) {

            thorium_actor_send_reply_empty(actor, ACTION_ASK_TO_STOP);
            thorium_actor_send_to_self_empty(actor, ACTION_ASK_TO_STOP);

            return;
        }

        /* migrate other actor
         */

        printf("actor %d asks actor %d to migrate using actor %d as spawner\n",
                        name, source, name);

        printf("Acquaintances of actor %d: ", name);
        core_vector_print_int(acquaintance_vector);
        printf("\n");

        thorium_actor_send_reply_int(actor, ACTION_MIGRATE, name);

        /* send a message to other while it is migrating.
         * this is supposed to work !
         */
        printf("actor %d sends ACTION_PING to %d while it is migrating\n",
                        name, source);
        thorium_actor_send_reply_empty(actor, ACTION_PING);

        concrete_actor->migrated_other = 1;

    } else if (tag == ACTION_MIGRATE_REPLY) {

        thorium_message_unpack_int(message, 0, &other);
        printf("actor %d received migrated actor %d\n", name, other);
        printf("Acquaintances of actor %d: ", name);
        core_vector_print_int(acquaintance_vector);
        printf("\n");

        /* it is possible that the ACTION_PING went through
         * before the migration
         */
        if (concrete_actor->pings == 2) {
            thorium_actor_send_reply_empty(actor, ACTION_ASK_TO_STOP);
            thorium_actor_send_to_self_empty(actor, ACTION_ASK_TO_STOP);
        }

    } else if (tag == ACTION_PACK) {

        thorium_actor_send_reply_int(actor, ACTION_PACK_REPLY, concrete_actor->value);

    } else if (tag == ACTION_UNPACK) {

        thorium_message_unpack_int(message, 0, &concrete_actor->value);
        thorium_actor_send_reply_empty(actor, ACTION_UNPACK_REPLY);

    } else if (tag == ACTION_ASK_TO_STOP) {

        printf("actor %d received ACTION_ASK_TO_STOP, value: %d ",
                        name, concrete_actor->value);
        printf("acquaintance vector: ");
        core_vector_print_int(acquaintance_vector);
        printf("\n");

        thorium_actor_send_to_self_empty(actor, ACTION_STOP);
    }
}
Ejemplo n.º 4
0
void thorium_worker_print_actors(struct thorium_worker *worker, struct thorium_balancer *scheduler)
{
    struct core_map_iterator iterator;
    int name;
    int count;
    struct thorium_actor *actor;
    int producers;
    int consumers;
    int received;
    int difference;
    int script;
    struct core_map distribution;
    int frequency;
    struct thorium_script *script_object;
    int dead;
    int node_name;
    int worker_name;
    int previous_amount;

    node_name = thorium_node_name(worker->node);
    worker_name = worker->name;

    core_map_iterator_init(&iterator, &worker->actors);

    printf("node/%d worker/%d %d queued messages, received: %d busy: %d load: %f ring: %d scheduled actors: %d/%d\n",
                    node_name, worker_name,
                    thorium_worker_get_scheduled_message_count(worker),
                    thorium_worker_get_sum_of_received_actor_messages(worker),
                    thorium_worker_is_busy(worker),
                    thorium_worker_get_scheduling_epoch_load(worker),
                    core_fast_ring_size_from_producer(&worker->actors_to_schedule),
                    thorium_scheduler_size(&worker->scheduler),
                    (int)core_map_size(&worker->actors));

    core_map_init(&distribution, sizeof(int), sizeof(int));

    while (core_map_iterator_get_next_key_and_value(&iterator, &name, NULL)) {

        actor = thorium_node_get_actor_from_name(worker->node, name);

        if (actor == NULL) {
            continue;
        }

        dead = thorium_actor_dead(actor);

        if (dead) {
            continue;
        }

        count = thorium_actor_get_mailbox_size(actor);
        received = thorium_actor_get_sum_of_received_messages(actor);
        producers = core_map_size(thorium_actor_get_received_messages(actor));
        consumers = core_map_size(thorium_actor_get_sent_messages(actor));
        previous_amount = 0;

        core_map_get_value(&worker->actor_received_messages, &name,
                        &previous_amount);
        difference = received - previous_amount;;

        if (!core_map_update_value(&worker->actor_received_messages, &name,
                        &received)) {
            core_map_add_value(&worker->actor_received_messages, &name, &received);
        }

        printf("  [%s/%d] mailbox: %d received: %d (+%d) producers: %d consumers: %d\n",
                        thorium_actor_script_name(actor),
                        name, count, received,
                       difference,
                       producers, consumers);

        script = thorium_actor_script(actor);

        if (core_map_get_value(&distribution, &script, &frequency)) {
            ++frequency;
            core_map_update_value(&distribution, &script, &frequency);
        } else {
            frequency = 1;
            core_map_add_value(&distribution, &script, &frequency);
        }
    }

    /*printf("\n");*/
    core_map_iterator_destroy(&iterator);

    core_map_iterator_init(&iterator, &distribution);

    printf("node/%d worker/%d Frequency list\n", node_name, worker_name);

    while (core_map_iterator_get_next_key_and_value(&iterator, &script, &frequency)) {

        script_object = thorium_node_find_script(worker->node, script);

        CORE_DEBUGGER_ASSERT(script_object != NULL);

        printf("node/%d worker/%d Frequency %s => %d\n",
                        node_name,
                        worker->name,
                        thorium_script_name(script_object),
                        frequency);
    }

    core_map_iterator_destroy(&iterator);
    core_map_destroy(&distribution);
}
Ejemplo n.º 5
0
void thorium_balancer_generate_symmetric_migrations(struct thorium_balancer *self, struct core_map *symmetric_actor_scripts,
                struct core_vector *migrations)
{
    int i;
    int worker_count;
    struct thorium_worker *worker;
    struct core_map *set;
    struct core_map_iterator iterator;
    struct thorium_migration migration;
    struct core_map script_current_worker;
    struct core_map script_current_worker_actor_count;
    int frequency;
    int current_worker;
    int current_worker_actor_count;
    int old_worker;
#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
    struct thorium_script *actual_script;
#endif
    struct thorium_node *node;
    int actor_name;
    int script;
    int new_worker;
    struct thorium_actor *actor;
    int enabled;

    /* Gather symmetric actors:
     */

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
    enabled = 1;
#else
    enabled = 0;
#endif

    core_map_init(&script_current_worker, sizeof(int), sizeof(int));
    core_map_init(&script_current_worker_actor_count, sizeof(int), sizeof(int));

    node = thorium_worker_pool_get_node(self->pool);
    worker_count = thorium_worker_pool_worker_count(self->pool);

    for (i = 0; i < worker_count; i++) {

        worker = thorium_worker_pool_get_worker(self->pool, i);

        set = thorium_worker_get_actors(worker);

        core_map_iterator_init(&iterator, set);

        while (core_map_iterator_get_next_key_and_value(&iterator, &actor_name, NULL)) {
            actor = thorium_node_get_actor_from_name(node, actor_name);

            if (actor == NULL) {
                continue;
            }

            script = thorium_actor_script(actor);

            /*
             * Check if the actor is symmetric
             */
            if (core_map_get_value(symmetric_actor_scripts, &script, &frequency)) {

                current_worker = 0;
                if (!core_map_get_value(&script_current_worker, &script, &current_worker)) {
                    core_map_add_value(&script_current_worker, &script, &current_worker);
                }
                current_worker_actor_count = 0;
                if (!core_map_get_value(&script_current_worker_actor_count, &script, &current_worker_actor_count)) {
                    core_map_add_value(&script_current_worker_actor_count, &script, &current_worker_actor_count);
                }

                /*
                 * Emit migration instruction
                 */

                old_worker = thorium_balancer_get_actor_worker(self, actor_name);
                new_worker = current_worker;
#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
                actual_script = thorium_node_find_script(node, script);
#endif

                if (enabled && old_worker != new_worker) {
                    thorium_migration_init(&migration, actor_name, old_worker, new_worker);
                    core_vector_push_back(migrations, &migration);
                    thorium_migration_destroy(&migration);

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
                    printf("[EMIT] ");
#endif
                } else {
#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
                    printf("[MOCK] ");
#endif
                }

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
                printf("SCHEDULER -> symmetric placement... %s/%d scheduled for execution on worker/%d of node/%d\n",
                                thorium_script_description(actual_script),
                                actor_name,
                                new_worker,
                                thorium_node_name(node));
#endif

                ++current_worker_actor_count;
                core_map_update_value(&script_current_worker_actor_count, &script, &current_worker_actor_count);

                /* The current worker is full.
                 * Increment the current worker and set the
                 * worker actor count to 0.
                 */
                if (current_worker_actor_count == frequency) {
                    ++current_worker;
                    core_map_update_value(&script_current_worker, &script, &current_worker);
                    current_worker_actor_count = 0;
                    core_map_update_value(&script_current_worker_actor_count, &script, &current_worker_actor_count);
                }
            }

        }

        core_map_iterator_destroy(&iterator);
    }

    core_map_destroy(&script_current_worker);
    core_map_destroy(&script_current_worker_actor_count);
}
Ejemplo n.º 6
0
void thorium_balancer_detect_symmetric_scripts(struct thorium_balancer *self, struct core_map *symmetric_actor_scripts)
{
    int i;
    struct thorium_worker *worker;
    struct thorium_actor *actor;
    struct core_map_iterator iterator;
    struct core_map *set;
    int actor_name;
    struct thorium_node *node;
    int script;
    int frequency;
    struct core_map frequencies;
    int worker_count;
    int population_per_worker;
#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
    struct thorium_script *actual_script;
#endif

    worker_count = thorium_worker_pool_worker_count(self->pool);
    core_map_init(&frequencies, sizeof(int), sizeof(int));

    node = thorium_worker_pool_get_node(self->pool);

    /* Gather frequencies
     */
    for (i = 0; i < worker_count; i++) {

        worker = thorium_worker_pool_get_worker(self->pool, i);

        set = thorium_worker_get_actors(worker);

        core_map_iterator_init(&iterator, set);

        while (core_map_iterator_get_next_key_and_value(&iterator, &actor_name, NULL)) {
            actor = thorium_node_get_actor_from_name(node, actor_name);

            if (actor == NULL) {
                continue;
            }
            script = thorium_actor_script(actor);

            frequency = 0;

            if (!core_map_get_value(&frequencies, &script, &frequency)) {
                core_map_add_value(&frequencies, &script, &frequency);
            }

            ++frequency;

            core_map_update_value(&frequencies, &script, &frequency);
        }

        core_map_iterator_destroy(&iterator);
    }

    /*
     * Detect symmetric scripts
     */
    core_map_iterator_init(&iterator, &frequencies);

    while (core_map_iterator_get_next_key_and_value(&iterator, &script, &frequency)) {

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
        actual_script = thorium_node_find_script(node, script);
#endif

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
        printf("SCHEDULER test symmetry %s %d\n",
                        thorium_script_description(actual_script),
                        frequency);
#endif

        if (frequency % worker_count == 0) {
            population_per_worker = frequency / worker_count;

            core_map_add_value(symmetric_actor_scripts, &script, &population_per_worker);

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
            printf("SCHEDULER: script %s is symmetric, worker_count: %d, population_per_worker: %d\n",
                            thorium_script_description(actual_script),
                            worker_count,
                            population_per_worker);
#endif
        }
    }

    core_map_iterator_destroy(&iterator);

    core_map_destroy(&frequencies);
}
Ejemplo n.º 7
0
void thorium_balancer_balance(struct thorium_balancer *self)
{
    /*
     * The 95th percentile is useful:
     * \see http://en.wikipedia.org/wiki/Burstable_billing
     * \see http://www.init7.net/en/backbone/95-percent-rule
     */
    int load_percentile_50;
    struct core_timer timer;

    int i;
    struct core_vector loads;
    struct core_vector loads_unsorted;
    struct core_vector burdened_workers;
    struct core_vector stalled_workers;
    struct thorium_worker *worker;
    struct thorium_node *node;

    /*struct core_set *set;*/
    struct core_pair pair;
    struct core_vector_iterator vector_iterator;
    int old_worker;
    int actor_name;
    int messages;
    int maximum;
    int with_maximum;
    struct core_map *set;
    struct core_map_iterator set_iterator;
    int stalled_index;
    int stalled_count;
    int new_worker_index;
    struct core_vector migrations;
    struct thorium_migration migration;
    struct thorium_migration *migration_to_do;
    struct thorium_actor *actor;
    int candidates;

    int load_value;
    int remaining_load;
    int projected_load;

    struct core_vector actors_to_migrate;
    int total;
    int with_messages;
    int stalled_percentile;
    int burdened_percentile;

    int old_total;
    int old_load;
    int new_load;
    int predicted_new_load;
    struct core_pair *pair_pointer;
    struct thorium_worker *new_worker;
    /*int new_total;*/
    int actor_load;

    int test_stalled_index;
    int tests;
    int found_match;
    int spawned_actors;
    int killed_actors;
    int perfect;

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
    struct core_map symmetric_actor_scripts;
    int script;
#endif

    node = thorium_worker_pool_get_node(self->pool);

    spawned_actors = thorium_node_get_counter(node, CORE_COUNTER_SPAWNED_ACTORS);

    /* There is nothing to balance...
     */
    if (spawned_actors == 0) {
        return;
    }

    killed_actors = thorium_node_get_counter(node, CORE_COUNTER_KILLED_ACTORS);

    /*
     * The system can probably not be balanced to get in
     * a better shape anyway.
     */
    if (spawned_actors == self->last_spawned_actors
                    && killed_actors == self->last_killed_actors
                    && self->last_migrations == 0) {

        printf("SCHEDULER: balance can not be improved because nothing changed.\n");
        return;
    }

    /* Check if we have perfection
     */

    perfect = 1;
    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {
        worker = thorium_worker_pool_get_worker(self->pool, i);

        load_value = thorium_worker_get_epoch_load(worker) * 100;

        if (load_value != 100) {
            perfect = 0;
            break;
        }
    }

    if (perfect) {
        printf("SCHEDULER: perfect balance can not be improved.\n");
        return;
    }

    /* update counters
     */
    self->last_spawned_actors = spawned_actors;
    self->last_killed_actors = killed_actors;

    /* Otherwise, try to balance things
     */
    core_timer_init(&timer);

    core_timer_start(&timer);

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
    core_map_init(&symmetric_actor_scripts, sizeof(int), sizeof(int));

    thorium_balancer_detect_symmetric_scripts(self, &symmetric_actor_scripts);
#endif

#ifdef THORIUM_WORKER_ENABLE_LOCK
    /* Lock all workers first
     */
    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {
        worker = thorium_worker_pool_get_worker(self->pool, i);

        thorium_worker_lock(worker);
    }
#endif

    core_vector_init(&migrations, sizeof(struct thorium_migration));

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
    printf("BALANCING\n");
#endif

    core_vector_init(&loads, sizeof(int));
    core_vector_init(&loads_unsorted, sizeof(int));
    core_vector_init(&burdened_workers, sizeof(struct core_pair));
    core_vector_init(&stalled_workers, sizeof(struct core_pair));

    core_vector_init(&actors_to_migrate, sizeof(struct core_pair));

    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {
        worker = thorium_worker_pool_get_worker(self->pool, i);
        load_value = thorium_worker_get_scheduling_epoch_load(worker) * SCHEDULER_PRECISION;

#if 0
        printf("DEBUG LOAD %d %d\n", i, load_value);
#endif

        core_vector_push_back(&loads, &load_value);
        core_vector_push_back(&loads_unsorted, &load_value);
    }

    core_vector_sort_int(&loads);

    stalled_percentile = core_statistics_get_percentile_int(&loads, SCHEDULER_WINDOW);
    /*load_percentile_25 = core_statistics_get_percentile_int(&loads, 25);*/
    load_percentile_50 = core_statistics_get_percentile_int(&loads, 50);
    /*load_percentile_75 = core_statistics_get_percentile_int(&loads, 75);*/
    burdened_percentile = core_statistics_get_percentile_int(&loads, 100 - SCHEDULER_WINDOW);

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
    printf("Percentiles for epoch loads: ");
    core_statistics_print_percentiles_int(&loads);
#endif

    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {
        worker = thorium_worker_pool_get_worker(self->pool, i);
        load_value = core_vector_at_as_int(&loads_unsorted, i);

        set = thorium_worker_get_actors(worker);

        if (stalled_percentile == burdened_percentile) {

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
            printf("scheduling_class:%s ",
                            THORIUM_CLASS_NORMAL_STRING);
#endif

        } else if (load_value <= stalled_percentile) {

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
            printf("scheduling_class:%s ",
                            THORIUM_CLASS_STALLED_STRING);
#endif

            core_pair_init(&pair, load_value, i);
            core_vector_push_back(&stalled_workers, &pair);

        } else if (load_value >= burdened_percentile) {

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
            printf("scheduling_class:%s ",
                            THORIUM_CLASS_BURDENED_STRING);
#endif

            core_pair_init(&pair, load_value, i);
            core_vector_push_back(&burdened_workers, &pair);
        } else {
#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
            printf("scheduling_class:%s ",
                            THORIUM_CLASS_NORMAL_STRING);
#endif
        }

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
        thorium_worker_print_actors(worker, self);
#endif

    }

    core_vector_sort_int_reverse(&burdened_workers);
    core_vector_sort_int(&stalled_workers);

    stalled_count = core_vector_size(&stalled_workers);

#ifdef THORIUM_SCHEDULER_ENABLE_VERBOSITY
    printf("MIGRATIONS (stalled: %d, burdened: %d)\n", (int)core_vector_size(&stalled_workers),
                    (int)core_vector_size(&burdened_workers));
#endif

    stalled_index = 0;
    core_vector_iterator_init(&vector_iterator, &burdened_workers);

    while (stalled_count > 0
                    && core_vector_iterator_get_next_value(&vector_iterator, &pair)) {

        old_worker = core_pair_get_second(&pair);

        worker = thorium_worker_pool_get_worker(self->pool, old_worker);
        set = thorium_worker_get_actors(worker);

        /*
        thorium_worker_print_actors(worker);
        printf("\n");
        */

        /*
         * Lock the worker and try to select actors for migration
         */
        core_map_iterator_init(&set_iterator, set);

        maximum = -1;
        with_maximum = 0;
        total = 0;
        with_messages = 0;

        while (core_map_iterator_get_next_key_and_value(&set_iterator, &actor_name, NULL)) {

            actor = thorium_node_get_actor_from_name(thorium_worker_pool_get_node(self->pool), actor_name);
            messages = thorium_balancer_get_actor_production(self, actor);

            if (maximum == -1 || messages > maximum) {
                maximum = messages;
                with_maximum = 1;
            } else if (messages == maximum) {
                with_maximum++;
            }

            if (messages > 0) {
                ++with_messages;
            }

            total += messages;
        }

        core_map_iterator_destroy(&set_iterator);

        core_map_iterator_init(&set_iterator, set);

        --with_maximum;

        candidates = 0;
        load_value = thorium_worker_get_scheduling_epoch_load(worker) * SCHEDULER_PRECISION;

        remaining_load = load_value;

#if 0
        printf("maximum %d with_maximum %d\n", maximum, with_maximum);
#endif

        while (core_map_iterator_get_next_key_and_value(&set_iterator, &actor_name, NULL)) {

            actor = thorium_node_get_actor_from_name(thorium_worker_pool_get_node(self->pool), actor_name);

            if (actor == NULL) {
                continue;
            }
            messages = thorium_balancer_get_actor_production(self, actor);

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
            script = thorium_actor_script(actor);


            /* symmetric actors are migrated elsewhere.
             */
            if (core_map_get_value(&symmetric_actor_scripts, &script, NULL)) {
                continue;
            }
#endif

            /* Simulate the remaining load
             */
            projected_load = remaining_load;
            projected_load -= ((0.0 + messages) / total) * load_value;

#ifdef THORIUM_SCHEDULER_DEBUG
            printf(" TESTING actor %d, production was %d, projected_load is %d (- %d * (1 - %d/%d)\n",
                            actor_name, messages, projected_load,
                            load_value, messages, total);
#endif

            /* An actor without any queued messages should not be migrated
             */
            if (messages > 0
                            && ((with_maximum > 0 && messages == maximum) || messages < maximum)
                /*
                 * Avoid removing too many actors because
                 * generating a stalled one is not desired
                 */
                    && (projected_load >= load_percentile_50

                /*
                 * The previous rule does not apply when there
                 * are 2 actors.
                 */
                   || with_messages == 2) ) {

                remaining_load = projected_load;

                candidates++;

                if (messages == maximum) {
                    --with_maximum;
                }


                core_pair_init(&pair, messages, actor_name);
                core_vector_push_back(&actors_to_migrate, &pair);

#ifdef THORIUM_SCHEDULER_DEBUG
                printf("early CANDIDATE for migration: actor %d, worker %d\n",
                                actor_name, old_worker);
#endif
            }
        }
        core_map_iterator_destroy(&set_iterator);

    }

    core_vector_iterator_destroy(&vector_iterator);

    /* Sort the candidates
     */

    /*
    core_vector_sort_int(&actors_to_migrate);

    printf("Percentiles for production: ");
    core_statistics_print_percentiles_int(&actors_to_migrate);
    */

    /* Sort them in reverse order.
     */
    core_vector_sort_int_reverse(&actors_to_migrate);

    core_vector_iterator_init(&vector_iterator, &actors_to_migrate);

    /* For each highly active actor,
     * try to match it with a stalled worker
     */
    while (core_vector_iterator_get_next_value(&vector_iterator, &pair)) {

        actor_name = core_pair_get_second(&pair);

        actor = thorium_node_get_actor_from_name(thorium_worker_pool_get_node(self->pool), actor_name);

        if (actor == NULL) {
           continue;
        }

        messages = thorium_balancer_get_actor_production(self, actor);
        old_worker = thorium_actor_assigned_worker(actor);

        worker = thorium_worker_pool_get_worker(self->pool, old_worker);

        /* old_total can not be 0 because otherwise the would not
         * be burdened.
         */
        old_total = thorium_worker_get_production(worker, self);
        with_messages = thorium_worker_get_producer_count(worker, self);
        old_load = thorium_worker_get_scheduling_epoch_load(worker) * SCHEDULER_PRECISION;
        actor_load = ((0.0 + messages) / old_total) * old_load;

        /* Try to find a stalled worker that can take it.
         */

        test_stalled_index = stalled_index;
        tests = 0;
        predicted_new_load = 0;

        found_match = 0;
        while (tests < stalled_count) {

            core_vector_get_value(&stalled_workers, test_stalled_index, &pair);
            new_worker_index = core_pair_get_second(&pair);

            new_worker = thorium_worker_pool_get_worker(self->pool, new_worker_index);
            new_load = thorium_worker_get_scheduling_epoch_load(new_worker) * SCHEDULER_PRECISION;
        /*new_total = thorium_worker_get_production(new_worker);*/

            predicted_new_load = new_load + actor_load;

            if (predicted_new_load > SCHEDULER_PRECISION /* && with_messages != 2 */) {
#ifdef THORIUM_SCHEDULER_DEBUG
                printf("Scheduler: skipping actor %d, predicted load is %d >= 100\n",
                           actor_name, predicted_new_load);
#endif

                ++tests;
                ++test_stalled_index;

                if (test_stalled_index == stalled_count) {
                    test_stalled_index = 0;
                }
                continue;
            }

            /* Otherwise, this stalled worker is fine...
             */
            stalled_index = test_stalled_index;
            found_match = 1;

            break;
        }

        /* This actor can not be migrated to any stalled worker.
         */
        if (!found_match) {
            continue;
        }

        /* Otherwise, update the load of the stalled one and go forward with the change.
         */

        pair_pointer = (struct core_pair *)core_vector_at(&stalled_workers, stalled_index);

        core_pair_set_first(pair_pointer, predicted_new_load);

        ++stalled_index;

        if (stalled_index == stalled_count) {
            stalled_index = 0;
        }


#if 0
        new_worker = thorium_worker_pool_get_worker(pool, new_worker_index);
        printf(" CANDIDATE: actor %d old worker %d (%d - %d = %d) new worker %d (%d + %d = %d)\n",
                        actor_name,
                        old_worker, value, messages, 2new_score,
                        new_worker_index, new_worker_old_score, messages, new_worker_new_score);
#endif

        thorium_migration_init(&migration, actor_name, old_worker, new_worker_index);
        core_vector_push_back(&migrations, &migration);
        thorium_migration_destroy(&migration);

    }

    core_vector_iterator_destroy(&vector_iterator);

    core_vector_destroy(&stalled_workers);
    core_vector_destroy(&burdened_workers);
    core_vector_destroy(&loads);
    core_vector_destroy(&loads_unsorted);
    core_vector_destroy(&actors_to_migrate);

    /* Update the last values
     */
    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {

        worker = thorium_worker_pool_get_worker(self->pool, i);

        set = thorium_worker_get_actors(worker);

        core_map_iterator_init(&set_iterator, set);

        while (core_map_iterator_get_next_key_and_value(&set_iterator, &actor_name, NULL)) {
            actor = thorium_node_get_actor_from_name(thorium_worker_pool_get_node(self->pool), actor_name);
            thorium_balancer_update_actor_production(self, actor);
        }
        core_map_iterator_destroy(&set_iterator);

        thorium_worker_reset_scheduling_epoch(worker);
    }

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
    /* Generate migrations for symmetric actors.
     */

    thorium_balancer_generate_symmetric_migrations(self, &symmetric_actor_scripts, &migrations);
#endif

    /* Actually do the migrations
     */
    core_vector_iterator_init(&vector_iterator, &migrations);

    while (core_vector_iterator_next(&vector_iterator, (void **)&migration_to_do)) {

        thorium_balancer_migrate(self, migration_to_do);
    }

    core_vector_iterator_destroy(&vector_iterator);

    self->last_migrations = core_vector_size(&migrations);

    core_vector_destroy(&migrations);

#ifdef THORIUM_WORKER_ENABLE_LOCK
    /* Unlock all workers
     */
    for (i = 0; i < thorium_worker_pool_worker_count(self->pool); i++) {
        worker = thorium_worker_pool_get_worker(self->pool, i);

        thorium_worker_unlock(worker);
    }
#endif

#ifdef THORIUM_SCHEDULER_ENABLE_SYMMETRIC_SCHEDULING
    core_map_destroy(&symmetric_actor_scripts);
#endif

    core_timer_stop(&timer);

    printf("SCHEDULER: elapsed time for balancing: %d us, %d migrations performed\n",
                    (int)(core_timer_get_elapsed_nanoseconds(&timer) / 1000),
                    self->last_migrations);
}