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         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 }