block/blk-mq-cpumap.c

   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         /*
  20          * Non present CPU will be mapped to queue index 0.
  21          */
  22         if (!cpu_present(cpu))
  23                 return 0;
  24         return cpu % nr_queues;
  25 }
  26
  27 static int get_first_sibling(unsigned int cpu)
  28 {
  29         unsigned int ret;
  30
  31         ret = cpumask_first(topology_sibling_cpumask(cpu));
  32         if (ret < nr_cpu_ids)
  33                 return ret;
  34
  35         return cpu;
  36 }
  37
  38 int blk_mq_map_queues(struct blk_mq_tag_set *set)
  39 {
  40         unsigned int *map = set->mq_map;
  41         unsigned int nr_queues = set->nr_hw_queues;
  42         unsigned int cpu, first_sibling;
  43
  44         for_each_possible_cpu(cpu) {
  45                 /*
  46                  * First do sequential mapping between CPUs and queues.
  47                  * In case we still have CPUs to map, and we have some number of
  48                  * threads per cores then map sibling threads to the same queue for
  49                  * performace optimizations.
  50                  */
  51                 if (cpu < nr_queues) {
  52                         map[cpu] = cpu_to_queue_index(nr_queues, cpu);
  53                 } else {
  54                         first_sibling = get_first_sibling(cpu);
  55                         if (first_sibling == cpu)
  56                                 map[cpu] = cpu_to_queue_index(nr_queues, cpu);
  57                         else
  58                                 map[cpu] = map[first_sibling];
  59                 }
  60         }
  61
  62         return 0;
  63 }
  64 EXPORT_SYMBOL_GPL(blk_mq_map_queues);
  65
  66 /*
  67  * We have no quick way of doing reverse lookups. This is only used at
  68  * queue init time, so runtime isn't important.
  69  */
  70 int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
  71 {
  72         int i;
  73
  74         for_each_possible_cpu(i) {
  75                 if (index == mq_map[i])
  76                         return local_memory_node(cpu_to_node(i));
  77         }
  78
  79         return NUMA_NO_NODE;
  80 }