tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 /*
20 * Non present CPU will be mapped to queue index 0.
21 */
22 if (!cpu_present(cpu))
23 return 0;
24 return cpu % nr_queues;
25}
26
27static int get_first_sibling(unsigned int cpu)
28{
29 unsigned int ret;
30
31 ret = cpumask_first(topology_sibling_cpumask(cpu));
32 if (ret < nr_cpu_ids)
33 return ret;
34
35 return cpu;
36}
37
38int blk_mq_map_queues(struct blk_mq_tag_set *set)
39{
40 unsigned int *map = set->mq_map;
41 unsigned int nr_queues = set->nr_hw_queues;
42 unsigned int cpu, first_sibling;
43
44 for_each_possible_cpu(cpu) {
45 /*
46 * First do sequential mapping between CPUs and queues.
47 * In case we still have CPUs to map, and we have some number of
48 * threads per cores then map sibling threads to the same queue for
49 * performace optimizations.
50 */
51 if (cpu < nr_queues) {
52 map[cpu] = cpu_to_queue_index(nr_queues, cpu);
53 } else {
54 first_sibling = get_first_sibling(cpu);
55 if (first_sibling == cpu)
56 map[cpu] = cpu_to_queue_index(nr_queues, cpu);
57 else
58 map[cpu] = map[first_sibling];
59 }
60 }
61
62 return 0;
63}
64EXPORT_SYMBOL_GPL(blk_mq_map_queues);
65
66/*
67 * We have no quick way of doing reverse lookups. This is only used at
68 * queue init time, so runtime isn't important.
69 */
70int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
71{
72 int i;
73
74 for_each_possible_cpu(i) {
75 if (index == mq_map[i])
76 return local_memory_node(cpu_to_node(i));
77 }
78
79 return NUMA_NO_NODE;
80}