// SPDX-License-Identifier: GPL-2.0 /* * CPU <-> hardware queue mapping helpers * * Copyright (C) 2013-2014 Jens Axboe */ #include <linux/kernel.h> #include <linux/threads.h> #include <linux/module.h> #include <linux/mm.h> #include <linux/smp.h> #include <linux/cpu.h> #include <linux/blk-mq.h> #include "blk.h" #include "blk-mq.h" static int queue_index(struct blk_mq_queue_map *qmap, unsigned int nr_queues, const int q) { return qmap->queue_offset + (q % nr_queues); } static int get_first_sibling(unsigned int cpu) { unsigned int ret; ret = cpumask_first(topology_sibling_cpumask(cpu)); if (ret < nr_cpu_ids) return ret; return cpu; } int blk_mq_map_queues(struct blk_mq_queue_map *qmap) { unsigned int *map = qmap->mq_map; unsigned int nr_queues = qmap->nr_queues; unsigned int cpu, first_sibling, q = 0; for_each_possible_cpu(cpu) map[cpu] = -1; /* * Spread queues among present CPUs first for minimizing * count of dead queues which are mapped by all un-present CPUs */ for_each_present_cpu(cpu) { if (q >= nr_queues) break; map[cpu] = queue_index(qmap, nr_queues, q++); } for_each_possible_cpu(cpu) { if (map[cpu] != -1) continue; /* * First do sequential mapping between CPUs and queues. * In case we still have CPUs to map, and we have some number of * threads per cores then map sibling threads to the same queue * for performance optimizations. */ if (q < nr_queues) { map[cpu] = queue_index(qmap, nr_queues, q++); } else { first_sibling = get_first_sibling(cpu); if (first_sibling == cpu) map[cpu] = queue_index(qmap, nr_queues, q++); else map[cpu] = map[first_sibling]; } } return 0; } EXPORT_SYMBOL_GPL(blk_mq_map_queues); /** * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index * @qmap: CPU to hardware queue map. * @index: hardware queue index. * * We have no quick way of doing reverse lookups. This is only used at * queue init time, so runtime isn't important. */ int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index) { int i; for_each_possible_cpu(i) { if (index == qmap->mq_map[i]) return cpu_to_node(i); } return NUMA_NO_NODE; }