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Commit 06f90dbd authored by Gregory Haskins's avatar Gregory Haskins Committed by Ingo Molnar
Browse files

sched: RT-balance, optimize 



We can cheaply track the number of bits set in the cpumask for the lowest
priority CPUs.  Therefore, compute the mask's weight and use it to skip
the optimal domain search logic when there is only one CPU available.

Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 17b3279b

kernel/sched_rt.c

+18 −7
Original line number Original line Diff line number Diff line
@@ -303,7 +303,7 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask) 
	int       cpu;

	int       cpu;

	cpumask_t *valid_mask = &__get_cpu_var(valid_cpu_mask);

	cpumask_t *valid_mask = &__get_cpu_var(valid_cpu_mask);

	int       lowest_prio = -1;

	int       lowest_prio = -1;

	int       ret         = 0;

	int       count       = 0;





	cpus_clear(*lowest_mask);

	cpus_clear(*lowest_mask);

	cpus_and(*valid_mask, cpu_online_map, task->cpus_allowed);

	cpus_and(*valid_mask, cpu_online_map, task->cpus_allowed);
@@ -316,7 +316,7 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask) 




		/* We look for lowest RT prio or non-rt CPU */

		/* We look for lowest RT prio or non-rt CPU */

		if (rq->rt.highest_prio >= MAX_RT_PRIO) {

		if (rq->rt.highest_prio >= MAX_RT_PRIO) {

			if (ret)

			if (count)

				cpus_clear(*lowest_mask);

				cpus_clear(*lowest_mask);

			cpu_set(rq->cpu, *lowest_mask);

			cpu_set(rq->cpu, *lowest_mask);

			return 1;

			return 1;
@@ -328,14 +328,17 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask) 
			if (rq->rt.highest_prio > lowest_prio) {

			if (rq->rt.highest_prio > lowest_prio) {

				/* new low - clear old data */

				/* new low - clear old data */

				lowest_prio = rq->rt.highest_prio;

				lowest_prio = rq->rt.highest_prio;

				if (count) {

					cpus_clear(*lowest_mask);

					cpus_clear(*lowest_mask);

					count = 0;

				}

			}

			}

			cpu_set(rq->cpu, *lowest_mask);

			cpu_set(rq->cpu, *lowest_mask);

			ret = 1;

			count++;

		}

		}

	}

	}





	return ret;

	return count;

}

}





static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)

static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
@@ -359,9 +362,17 @@ static int find_lowest_rq(struct task_struct *task) 
	cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);

	cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);

	int this_cpu = smp_processor_id();

	int this_cpu = smp_processor_id();

	int cpu      = task_cpu(task);

	int cpu      = task_cpu(task);

	int count    = find_lowest_cpus(task, lowest_mask);





	if (!find_lowest_cpus(task, lowest_mask))

	if (!count)

		return -1;

		return -1; /* No targets found */



	/*

	 * There is no sense in performing an optimal search if only one

	 * target is found.

	 */

	if (count == 1)

		return first_cpu(*lowest_mask);





	/*

	/*

	 * At this point we have built a mask of cpus representing the

	 * At this point we have built a mask of cpus representing the