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(struct blk_mq_queue_map *qmap, 18 unsigned int nr_queues, const int cpu) 19 { 20 return qmap->queue_offset + (cpu % nr_queues); 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_queue_map *qmap) 35 { 36 unsigned int *map = qmap->mq_map; 37 unsigned int nr_queues = qmap->nr_queues; 38 unsigned int cpu, first_sibling; 39 40 for_each_possible_cpu(cpu) { 41 /* 42 * First do sequential mapping between CPUs and queues. 43 * In case we still have CPUs to map, and we have some number of 44 * threads per cores then map sibling threads to the same queue for 45 * performace optimizations. 46 */ 47 if (cpu < nr_queues) { 48 map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu); 49 } else { 50 first_sibling = get_first_sibling(cpu); 51 if (first_sibling == cpu) 52 map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu); 53 else 54 map[cpu] = map[first_sibling]; 55 } 56 } 57 58 return 0; 59 } 60 EXPORT_SYMBOL_GPL(blk_mq_map_queues); 61 62 /* 63 * We have no quick way of doing reverse lookups. This is only used at 64 * queue init time, so runtime isn't important. 65 */ 66 int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index) 67 { 68 int i; 69 70 for_each_possible_cpu(i) { 71 if (index == qmap->mq_map[i]) 72 return local_memory_node(cpu_to_node(i)); 73 } 74 75 return NUMA_NO_NODE; 76 } 77