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 12 static 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 21 static 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 27 static 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 38 int 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 93 unsigned 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 } 109