block/blk-mq-cpumap.c

   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 cpu_to_queue_index(struct blk_mq_queue_map *qmap,
  19                               unsigned int nr_queues, const int cpu)
  20 {
  21         return qmap->queue_offset + (cpu % 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;
  40
  41         for_each_possible_cpu(cpu) {
  42                 /*
  43                  * First do sequential mapping between CPUs and queues.
  44                  * In case we still have CPUs to map, and we have some number of
  45                  * threads per cores then map sibling threads to the same queue
  46                  * for performance optimizations.
  47                  */
  48                 if (cpu < nr_queues) {
  49                         map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu);
  50                 } else {
  51                         first_sibling = get_first_sibling(cpu);
  52                         if (first_sibling == cpu)
  53                                 map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu);
  54                         else
  55                                 map[cpu] = map[first_sibling];
  56                 }
  57         }
  58
  59         return 0;
  60 }
  61 EXPORT_SYMBOL_GPL(blk_mq_map_queues);
  62
  63 /**
  64  * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
  65  * @qmap: CPU to hardware queue map.
  66  * @index: hardware queue index.
  67  *
  68  * We have no quick way of doing reverse lookups. This is only used at
  69  * queue init time, so runtime isn't important.
  70  */
  71 int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
  72 {
  73         int i;
  74
  75         for_each_possible_cpu(i) {
  76                 if (index == qmap->mq_map[i])
  77                         return local_memory_node(cpu_to_node(i));
  78         }
  79
  80         return NUMA_NO_NODE;
  81 }