1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * CPU <-> hardware queue mapping helpers 4 * 5 * Copyright (C) 2013-2014 Jens Axboe 6 */ 7 #include <linux/kernel.h> 8 #include <linux/threads.h> 9 #include <linux/module.h> 10 #include <linux/mm.h> 11 #include <linux/smp.h> 12 #include <linux/cpu.h> 13 14 #include <linux/blk-mq.h> 15 #include "blk.h" 16 #include "blk-mq.h" 17 18 static int queue_index(struct blk_mq_queue_map *qmap, 19 unsigned int nr_queues, const int q) 20 { 21 return qmap->queue_offset + (q % nr_queues); 22 } 23 24 static int get_first_sibling(unsigned int cpu) 25 { 26 unsigned int ret; 27 28 ret = cpumask_first(topology_sibling_cpumask(cpu)); 29 if (ret < nr_cpu_ids) 30 return ret; 31 32 return cpu; 33 } 34 35 int blk_mq_map_queues(struct blk_mq_queue_map *qmap) 36 { 37 unsigned int *map = qmap->mq_map; 38 unsigned int nr_queues = qmap->nr_queues; 39 unsigned int cpu, first_sibling, q = 0; 40 41 for_each_possible_cpu(cpu) 42 map[cpu] = -1; 43 44 /* 45 * Spread queues among present CPUs first for minimizing 46 * count of dead queues which are mapped by all un-present CPUs 47 */ 48 for_each_present_cpu(cpu) { 49 if (q >= nr_queues) 50 break; 51 map[cpu] = queue_index(qmap, nr_queues, q++); 52 } 53 54 for_each_possible_cpu(cpu) { 55 if (map[cpu] != -1) 56 continue; 57 /* 58 * First do sequential mapping between CPUs and queues. 59 * In case we still have CPUs to map, and we have some number of 60 * threads per cores then map sibling threads to the same queue 61 * for performance optimizations. 62 */ 63 if (q < nr_queues) { 64 map[cpu] = queue_index(qmap, nr_queues, q++); 65 } else { 66 first_sibling = get_first_sibling(cpu); 67 if (first_sibling == cpu) 68 map[cpu] = queue_index(qmap, nr_queues, q++); 69 else 70 map[cpu] = map[first_sibling]; 71 } 72 } 73 74 return 0; 75 } 76 EXPORT_SYMBOL_GPL(blk_mq_map_queues); 77 78 /** 79 * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index 80 * @qmap: CPU to hardware queue map. 81 * @index: hardware queue index. 82 * 83 * We have no quick way of doing reverse lookups. This is only used at 84 * queue init time, so runtime isn't important. 85 */ 86 int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index) 87 { 88 int i; 89 90 for_each_possible_cpu(i) { 91 if (index == qmap->mq_map[i]) 92 return local_memory_node(cpu_to_node(i)); 93 } 94 95 return NUMA_NO_NODE; 96 } 97