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_cpus, unsigned int nr_queues,
 18			      const int cpu)
 19{
 20	return cpu * nr_queues / nr_cpus;
 21}
 22
 23static int get_first_sibling(unsigned int cpu)
 24{
 25	unsigned int ret;
 26
 27	ret = cpumask_first(topology_sibling_cpumask(cpu));
 28	if (ret < nr_cpu_ids)
 29		return ret;
 30
 31	return cpu;
 32}
 33
 34int blk_mq_map_queues(struct blk_mq_tag_set *set)
 35{
 36	unsigned int *map = set->mq_map;
 37	unsigned int nr_queues = set->nr_hw_queues;
 38	const struct cpumask *online_mask = cpu_online_mask;
 39	unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
 40	cpumask_var_t cpus;
 41
 42	if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
 43		return -ENOMEM;
 44
 45	cpumask_clear(cpus);
 46	nr_cpus = nr_uniq_cpus = 0;
 47	for_each_cpu(i, online_mask) {
 48		nr_cpus++;
 49		first_sibling = get_first_sibling(i);
 50		if (!cpumask_test_cpu(first_sibling, cpus))
 51			nr_uniq_cpus++;
 52		cpumask_set_cpu(i, cpus);
 53	}
 54
 55	queue = 0;
 56	for_each_possible_cpu(i) {
 57		if (!cpumask_test_cpu(i, online_mask)) {
 58			map[i] = 0;
 59			continue;
 60		}
 61
 62		/*
 63		 * Easy case - we have equal or more hardware queues. Or
 64		 * there are no thread siblings to take into account. Do
 65		 * 1:1 if enough, or sequential mapping if less.
 
 66		 */
 67		if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
 68			map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
 69			queue++;
 70			continue;
 
 
 
 
 71		}
 72
 73		/*
 74		 * Less then nr_cpus queues, and we have some number of
 75		 * threads per cores. Map sibling threads to the same
 76		 * queue.
 77		 */
 78		first_sibling = get_first_sibling(i);
 79		if (first_sibling == i) {
 80			map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
 81							queue);
 82			queue++;
 83		} else
 84			map[i] = map[first_sibling];
 85	}
 86
 87	free_cpumask_var(cpus);
 88	return 0;
 89}
 90EXPORT_SYMBOL_GPL(blk_mq_map_queues);
 91
 92/*
 
 
 
 
 93 * We have no quick way of doing reverse lookups. This is only used at
 94 * queue init time, so runtime isn't important.
 95 */
 96int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
 97{
 98	int i;
 99
100	for_each_possible_cpu(i) {
101		if (index == mq_map[i])
102			return local_memory_node(cpu_to_node(i));
103	}
104
105	return NUMA_NO_NODE;
106}