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(struct blk_mq_queue_map *qmap,
  18                               unsigned int nr_queues, const int cpu)
  19 {
  20         return qmap->queue_offset + (cpu % nr_queues);
  21 }
  22
  23 static int get_first_sibling(unsigned int cpu)
  24 {
  25         unsigned int ret;
  26
  27         ret = cpumask_first(topology_sibling_cpumask(cpu));
  28         if (ret < nr_cpu_ids)
  29                 return ret;
  30
  31         return cpu;
  32 }
  33
  34 int blk_mq_map_queues(struct blk_mq_queue_map *qmap)
  35 {
  36         unsigned int *map = qmap->mq_map;
  37         unsigned int nr_queues = qmap->nr_queues;
  38         unsigned int cpu, first_sibling;
  39
  40         for_each_possible_cpu(cpu) {
  41                 /*
  42                  * First do sequential mapping between CPUs and queues.
  43                  * In case we still have CPUs to map, and we have some number of
  44                  * threads per cores then map sibling threads to the same queue for
  45                  * performace optimizations.
  46                  */
  47                 if (cpu < nr_queues) {
  48                         map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu);
  49                 } else {
  50                         first_sibling = get_first_sibling(cpu);
  51                         if (first_sibling == cpu)
  52                                 map[cpu] = cpu_to_queue_index(qmap, nr_queues, cpu);
  53                         else
  54                                 map[cpu] = map[first_sibling];
  55                 }
  56         }
  57
  58         return 0;
  59 }
  60 EXPORT_SYMBOL_GPL(blk_mq_map_queues);
  61
  62 /*
  63  * We have no quick way of doing reverse lookups. This is only used at
  64  * queue init time, so runtime isn't important.
  65  */
  66 int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
  67 {
  68         int i;
  69
  70         for_each_possible_cpu(i) {
  71                 if (index == qmap->mq_map[i])
  72                         return local_memory_node(cpu_to_node(i));
  73         }
  74
  75         return NUMA_NO_NODE;
  76 }