LXR linux/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
  17static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
  18                              const int cpu)
  19{
  20        return cpu * nr_queues / nr_cpus;
  21}
  22
  23static 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
  34int blk_mq_map_queues(struct blk_mq_tag_set *set)
  35{
  36        unsigned int *map = set->mq_map;
  37        unsigned int nr_queues = set->nr_hw_queues;
  38        const struct cpumask *online_mask = cpu_online_mask;
  39        unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
  40        cpumask_var_t cpus;
  41
  42        if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
  43                return -ENOMEM;
  44
  45        cpumask_clear(cpus);
  46        nr_cpus = nr_uniq_cpus = 0;
  47        for_each_cpu(i, online_mask) {
  48                nr_cpus++;
  49                first_sibling = get_first_sibling(i);
  50                if (!cpumask_test_cpu(first_sibling, cpus))
  51                        nr_uniq_cpus++;
  52                cpumask_set_cpu(i, cpus);
  53        }
  54
  55        queue = 0;
  56        for_each_possible_cpu(i) {
  57                if (!cpumask_test_cpu(i, online_mask)) {
  58                        map[i] = 0;
  59                        continue;
  60                }
  61
  62                /*
  63                 * Easy case - we have equal or more hardware queues. Or
  64                 * there are no thread siblings to take into account. Do
  65                 * 1:1 if enough, or sequential mapping if less.
  66                 */
  67                if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
  68                        map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
  69                        queue++;
  70                        continue;
  71                }
  72
  73                /*
  74                 * Less then nr_cpus queues, and we have some number of
  75                 * threads per cores. Map sibling threads to the same
  76                 * queue.
  77                 */
  78                first_sibling = get_first_sibling(i);
  79                if (first_sibling == i) {
  80                        map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
  81                                                        queue);
  82                        queue++;
  83                } else
  84                        map[i] = map[first_sibling];
  85        }
  86
  87        free_cpumask_var(cpus);
  88        return 0;
  89}
  90
  91/*
  92 * We have no quick way of doing reverse lookups. This is only used at
  93 * queue init time, so runtime isn't important.
  94 */
  95int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
  96{
  97        int i;
  98
  99        for_each_possible_cpu(i) {
 100                if (index == mq_map[i])
 101                        return local_memory_node(cpu_to_node(i));
 102        }
 103
 104        return NUMA_NO_NODE;
 105}
 106