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_queues, const int cpu) 18 { 19 /* 20 * Non online CPU will be mapped to queue index 0. 21 */ 22 if (!cpu_online(cpu)) 23 return 0; 24 return cpu % nr_queues; 25 } 26 27 static int get_first_sibling(unsigned int cpu) 28 { 29 unsigned int ret; 30 31 ret = cpumask_first(topology_sibling_cpumask(cpu)); 32 if (ret < nr_cpu_ids) 33 return ret; 34 35 return cpu; 36 } 37 38 int blk_mq_map_queues(struct blk_mq_tag_set *set) 39 { 40 unsigned int *map = set->mq_map; 41 unsigned int nr_queues = set->nr_hw_queues; 42 unsigned int cpu, first_sibling; 43 44 for_each_possible_cpu(cpu) { 45 /* 46 * First do sequential mapping between CPUs and queues. 47 * In case we still have CPUs to map, and we have some number of 48 * threads per cores then map sibling threads to the same queue for 49 * performace optimizations. 50 */ 51 if (cpu < nr_queues) { 52 map[cpu] = cpu_to_queue_index(nr_queues, cpu); 53 } else { 54 first_sibling = get_first_sibling(cpu); 55 if (first_sibling == cpu) 56 map[cpu] = cpu_to_queue_index(nr_queues, cpu); 57 else 58 map[cpu] = map[first_sibling]; 59 } 60 } 61 62 return 0; 63 } 64 EXPORT_SYMBOL_GPL(blk_mq_map_queues); 65 66 /* 67 * We have no quick way of doing reverse lookups. This is only used at 68 * queue init time, so runtime isn't important. 69 */ 70 int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index) 71 { 72 int i; 73 74 for_each_possible_cpu(i) { 75 if (index == mq_map[i]) 76 return local_memory_node(cpu_to_node(i)); 77 } 78 79 return NUMA_NO_NODE; 80 } 81