1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * CPU <-> hardware queue mapping helpers
 4 *
 5 * Copyright (C) 2013-2014 Jens Axboe
 6 */
 7#include <linux/kernel.h>
 8#include <linux/threads.h>
 9#include <linux/module.h>
10#include <linux/mm.h>
11#include <linux/smp.h>
12#include <linux/cpu.h>
13
14#include <linux/blk-mq.h>
15#include "blk.h"
16#include "blk-mq.h"
17
18static int queue_index(struct blk_mq_queue_map *qmap,
19		       unsigned int nr_queues, const int q)
20{
21	return qmap->queue_offset + (q % nr_queues);
22}
23
24static int get_first_sibling(unsigned int cpu)
25{
26	unsigned int ret;
27
28	ret = cpumask_first(topology_sibling_cpumask(cpu));
29	if (ret < nr_cpu_ids)
30		return ret;
31
32	return cpu;
33}
34
35void blk_mq_map_queues(struct blk_mq_queue_map *qmap)
36{
37	unsigned int *map = qmap->mq_map;
38	unsigned int nr_queues = qmap->nr_queues;
39	unsigned int cpu, first_sibling, q = 0;
40
41	for_each_possible_cpu(cpu)
42		map[cpu] = -1;
43
44	/*
45	 * Spread queues among present CPUs first for minimizing
46	 * count of dead queues which are mapped by all un-present CPUs
47	 */
48	for_each_present_cpu(cpu) {
49		if (q >= nr_queues)
50			break;
51		map[cpu] = queue_index(qmap, nr_queues, q++);
52	}
53
54	for_each_possible_cpu(cpu) {
55		if (map[cpu] != -1)
56			continue;
57		/*
58		 * First do sequential mapping between CPUs and queues.
59		 * In case we still have CPUs to map, and we have some number of
60		 * threads per cores then map sibling threads to the same queue
61		 * for performance optimizations.
62		 */
63		if (q < nr_queues) {
64			map[cpu] = queue_index(qmap, nr_queues, q++);
65		} else {
66			first_sibling = get_first_sibling(cpu);
67			if (first_sibling == cpu)
68				map[cpu] = queue_index(qmap, nr_queues, q++);
69			else
70				map[cpu] = map[first_sibling];
71		}
72	}
 
 
73}
74EXPORT_SYMBOL_GPL(blk_mq_map_queues);
75
76/**
77 * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
78 * @qmap: CPU to hardware queue map.
79 * @index: hardware queue index.
80 *
81 * We have no quick way of doing reverse lookups. This is only used at
82 * queue init time, so runtime isn't important.
83 */
84int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
85{
86	int i;
87
88	for_each_possible_cpu(i) {
89		if (index == qmap->mq_map[i])
90			return cpu_to_node(i);
91	}
92
93	return NUMA_NO_NODE;
94}

 
 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}