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
queue_index(struct blk_mq_queue_map * qmap,unsigned int nr_queues,const int q)18 static 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
get_first_sibling(unsigned int cpu)24 static 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
blk_mq_map_queues(struct blk_mq_queue_map * qmap)35 int 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
74 return 0;
75 }
76 EXPORT_SYMBOL_GPL(blk_mq_map_queues);
77
78 /**
79 * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
80 * @qmap: CPU to hardware queue map.
81 * @index: hardware queue index.
82 *
83 * We have no quick way of doing reverse lookups. This is only used at
84 * queue init time, so runtime isn't important.
85 */
blk_mq_hw_queue_to_node(struct blk_mq_queue_map * qmap,unsigned int index)86 int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
87 {
88 int i;
89
90 for_each_possible_cpu(i) {
91 if (index == qmap->mq_map[i])
92 return cpu_to_node(i);
93 }
94
95 return NUMA_NO_NODE;
96 }
97