move_tasks()详解

KERNEL VERSION: linux-2.6.34

[load_balance() > move_tasks()]

move_tasks tries to move up to max_load_move weighted load from busiest to this_rq, as part of a balancing operation within domain "sd".Returns 1 if successful and 0 otherwise.Called with both runqueues locked.
 

static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest, unsigned long max_load_move, struct sched_domain *sd, enum cpu_idle_type idle, int *all_pinned)
{
    unsigned long total_load_moved = 0, load_moved;
    int this_best_prio = this_rq->curr->prio;

    do {
        load_moved = load_balance_fair(this_rq, this_cpu, busiest,
                max_load_move - total_load_moved,
                sd, idle, all_pinned, &this_best_prio);

        total_load_moved += load_moved;

#ifdef CONFIG_PREEMPT
        /*
         * NEWIDLE balancing is a source of latency, so preemptible
         * kernels will stop after the first task is pulled to minimize
         * the critical section.
         */
        if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
            break;

        if (raw_spin_is_contended(&this_rq->lock) ||
                raw_spin_is_contended(&busiest->lock))
            break;
#endif
    } while (load_moved && max_load_move > total_load_moved);

    return total_load_moved > 0;
}