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