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 17 static 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 23 static 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 34 int 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 } 90 91 /* 92 * We have no quick way of doing reverse lookups. This is only used at 93 * queue init time, so runtime isn't important. 94 */ 95 int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index) 96 { 97 int i; 98 99 for_each_possible_cpu(i) { 100 if (index == mq_map[i]) 101 return local_memory_node(cpu_to_node(i)); 102 } 103 104 return NUMA_NO_NODE; 105 } 106