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 
cpu_to_queue_index(unsigned int nr_queues,const int cpu)17 static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
18 {
19 	return cpu % nr_queues;
20 }
21 
get_first_sibling(unsigned int cpu)22 static 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 
blk_mq_map_queues(struct blk_mq_tag_set * set)33 int 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 }
59 EXPORT_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  */
blk_mq_hw_queue_to_node(unsigned int * mq_map,unsigned int index)65 int 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 }
76