1/*
 2 * CPU <-> hardware queue mapping helpers
 3 *
 4 * Copyright (C) 2013-2014 Jens Axboe
 5 */
 6#include <linux/kernel.h>
 7#include <linux/threads.h>
 8#include <linux/module.h>
 9#include <linux/mm.h>
10#include <linux/smp.h>
11#include <linux/cpu.h>
12
13#include <linux/blk-mq.h>
14#include "blk.h"
15#include "blk-mq.h"
16
17static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
18{
19	return cpu % nr_queues;
20}
21
22static int get_first_sibling(unsigned int cpu)
23{
24	unsigned int ret;
25
26	ret = cpumask_first(topology_sibling_cpumask(cpu));
27	if (ret < nr_cpu_ids)
28		return ret;
29
30	return cpu;
31}
32
33int blk_mq_map_queues(struct blk_mq_tag_set *set)
34{
35	unsigned int *map = set->mq_map;
36	unsigned int nr_queues = set->nr_hw_queues;
37	unsigned int cpu, first_sibling;
38
39	for_each_possible_cpu(cpu) {
40		/*
41		 * First do sequential mapping between CPUs and queues.
42		 * In case we still have CPUs to map, and we have some number of
43		 * threads per cores then map sibling threads to the same queue for
44		 * performace optimizations.
45		 */
46		if (cpu < nr_queues) {
47			map[cpu] = cpu_to_queue_index(nr_queues, cpu);
48		} else {
49			first_sibling = get_first_sibling(cpu);
50			if (first_sibling == cpu)
51				map[cpu] = cpu_to_queue_index(nr_queues, cpu);
52			else
53				map[cpu] = map[first_sibling];
54		}
55	}
56
57	return 0;
58}
59EXPORT_SYMBOL_GPL(blk_mq_map_queues);
60
61/*
62 * We have no quick way of doing reverse lookups. This is only used at
63 * queue init time, so runtime isn't important.
64 */
65int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
66{
67	int i;
68
69	for_each_possible_cpu(i) {
70		if (index == mq_map[i])
71			return local_memory_node(cpu_to_node(i));
72	}
73
74	return NUMA_NO_NODE;
75}