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_update_queue_map(unsigned int *map, unsigned int nr_queues, 35 const struct cpumask *online_mask) 36 { 37 unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling; 38 cpumask_var_t cpus; 39 40 if (!alloc_cpumask_var(&cpus, GFP_ATOMIC)) 41 return 1; 42 43 cpumask_clear(cpus); 44 nr_cpus = nr_uniq_cpus = 0; 45 for_each_cpu(i, online_mask) { 46 nr_cpus++; 47 first_sibling = get_first_sibling(i); 48 if (!cpumask_test_cpu(first_sibling, cpus)) 49 nr_uniq_cpus++; 50 cpumask_set_cpu(i, cpus); 51 } 52 53 queue = 0; 54 for_each_possible_cpu(i) { 55 if (!cpumask_test_cpu(i, online_mask)) { 56 map[i] = 0; 57 continue; 58 } 59 60 /* 61 * Easy case - we have equal or more hardware queues. Or 62 * there are no thread siblings to take into account. Do 63 * 1:1 if enough, or sequential mapping if less. 64 */ 65 if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) { 66 map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue); 67 queue++; 68 continue; 69 } 70 71 /* 72 * Less then nr_cpus queues, and we have some number of 73 * threads per cores. Map sibling threads to the same 74 * queue. 75 */ 76 first_sibling = get_first_sibling(i); 77 if (first_sibling == i) { 78 map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues, 79 queue); 80 queue++; 81 } else 82 map[i] = map[first_sibling]; 83 } 84 85 free_cpumask_var(cpus); 86 return 0; 87 } 88 89 unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set) 90 { 91 unsigned int *map; 92 93 /* If cpus are offline, map them to first hctx */ 94 map = kzalloc_node(sizeof(*map) * nr_cpu_ids, GFP_KERNEL, 95 set->numa_node); 96 if (!map) 97 return NULL; 98 99 if (!blk_mq_update_queue_map(map, set->nr_hw_queues, cpu_online_mask)) 100 return map; 101 102 kfree(map); 103 return NULL; 104 } 105 106 /* 107 * We have no quick way of doing reverse lookups. This is only used at 108 * queue init time, so runtime isn't important. 109 */ 110 int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index) 111 { 112 int i; 113 114 for_each_possible_cpu(i) { 115 if (index == mq_map[i]) 116 return cpu_to_node(i); 117 } 118 119 return NUMA_NO_NODE; 120 } 121