tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1#include <linux/kernel.h>
2#include <linux/threads.h>
3#include <linux/module.h>
4#include <linux/mm.h>
5#include <linux/smp.h>
6#include <linux/cpu.h>
7
8#include <linux/blk-mq.h>
9#include "blk.h"
10#include "blk-mq.h"
11
12static void show_map(unsigned int *map, unsigned int nr)
13{
14 int i;
15
16 pr_info("blk-mq: CPU -> queue map\n");
17 for_each_online_cpu(i)
18 pr_info(" CPU%2u -> Queue %u\n", i, map[i]);
19}
20
21static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
22 const int cpu)
23{
24 return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
25}
26
27static int get_first_sibling(unsigned int cpu)
28{
29 unsigned int ret;
30
31 ret = cpumask_first(topology_thread_cpumask(cpu));
32 if (ret < nr_cpu_ids)
33 return ret;
34
35 return cpu;
36}
37
38int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
39{
40 unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
41 cpumask_var_t cpus;
42
43 if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
44 return 1;
45
46 cpumask_clear(cpus);
47 nr_cpus = nr_uniq_cpus = 0;
48 for_each_online_cpu(i) {
49 nr_cpus++;
50 first_sibling = get_first_sibling(i);
51 if (!cpumask_test_cpu(first_sibling, cpus))
52 nr_uniq_cpus++;
53 cpumask_set_cpu(i, cpus);
54 }
55
56 queue = 0;
57 for_each_possible_cpu(i) {
58 if (!cpu_online(i)) {
59 map[i] = 0;
60 continue;
61 }
62
63 /*
64 * Easy case - we have equal or more hardware queues. Or
65 * there are no thread siblings to take into account. Do
66 * 1:1 if enough, or sequential mapping if less.
67 */
68 if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
69 map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
70 queue++;
71 continue;
72 }
73
74 /*
75 * Less then nr_cpus queues, and we have some number of
76 * threads per cores. Map sibling threads to the same
77 * queue.
78 */
79 first_sibling = get_first_sibling(i);
80 if (first_sibling == i) {
81 map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
82 queue);
83 queue++;
84 } else
85 map[i] = map[first_sibling];
86 }
87
88 show_map(map, nr_cpus);
89 free_cpumask_var(cpus);
90 return 0;
91}
92
93unsigned int *blk_mq_make_queue_map(struct blk_mq_reg *reg)
94{
95 unsigned int *map;
96
97 /* If cpus are offline, map them to first hctx */
98 map = kzalloc_node(sizeof(*map) * num_possible_cpus(), GFP_KERNEL,
99 reg->numa_node);
100 if (!map)
101 return NULL;
102
103 if (!blk_mq_update_queue_map(map, reg->nr_hw_queues))
104 return map;
105
106 kfree(map);
107 return NULL;
108}