blk-mq-cpumap.c 1.62 KB
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/*
 * CPU <-> hardware queue mapping helpers
 *
 * Copyright (C) 2013-2014 Jens Axboe
 */
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#include <linux/kernel.h>
#include <linux/threads.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/cpu.h>

#include <linux/blk-mq.h>
#include "blk.h"
#include "blk-mq.h"

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static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
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{
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	return cpu % nr_queues;
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}

static int get_first_sibling(unsigned int cpu)
{
	unsigned int ret;

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	ret = cpumask_first(topology_sibling_cpumask(cpu));
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	if (ret < nr_cpu_ids)
		return ret;

	return cpu;
}

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int blk_mq_map_queues(struct blk_mq_tag_set *set)
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{
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	unsigned int *map = set->mq_map;
	unsigned int nr_queues = set->nr_hw_queues;
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	unsigned int cpu, first_sibling;
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	for_each_possible_cpu(cpu) {
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		/*
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		 * First do sequential mapping between CPUs and queues.
		 * In case we still have CPUs to map, and we have some number of
		 * threads per cores then map sibling threads to the same queue for
		 * performace optimizations.
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		 */
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		if (cpu < nr_queues) {
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			map[cpu] = cpu_to_queue_index(nr_queues, cpu);
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		} else {
			first_sibling = get_first_sibling(cpu);
			if (first_sibling == cpu)
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				map[cpu] = cpu_to_queue_index(nr_queues, cpu);
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			else
				map[cpu] = map[first_sibling];
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		}
	}

	return 0;
}
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EXPORT_SYMBOL_GPL(blk_mq_map_queues);
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/*
 * We have no quick way of doing reverse lookups. This is only used at
 * queue init time, so runtime isn't important.
 */
int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
{
	int i;

	for_each_possible_cpu(i) {
		if (index == mq_map[i])
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			return local_memory_node(cpu_to_node(i));
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	}

	return NUMA_NO_NODE;
}