block/blk-mq-cpumap.c

   1 #include <linux/kernel.h>
   2 #include <linux/threads.h>
   3 #include <linux/module.h>
   4 #include <linux/mm.h>
   5 #include <linux/smp.h>
   6 #include <linux/cpu.h>
   7
   8 #include <linux/blk-mq.h>
   9 #include "blk.h"
  10 #include "blk-mq.h"
  11
  12 static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
  13                               const int cpu)
  14 {
  15         return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
  16 }
  17
  18 static int get_first_sibling(unsigned int cpu)
  19 {
  20         unsigned int ret;
  21
  22         ret = cpumask_first(topology_thread_cpumask(cpu));
  23         if (ret < nr_cpu_ids)
  24                 return ret;
  25
  26         return cpu;
  27 }
  28
  29 int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
  30 {
  31         unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
  32         cpumask_var_t cpus;
  33
  34         if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
  35                 return 1;
  36
  37         cpumask_clear(cpus);
  38         nr_cpus = nr_uniq_cpus = 0;
  39         for_each_online_cpu(i) {
  40                 nr_cpus++;
  41                 first_sibling = get_first_sibling(i);
  42                 if (!cpumask_test_cpu(first_sibling, cpus))
  43                         nr_uniq_cpus++;
  44                 cpumask_set_cpu(i, cpus);
  45         }
  46
  47         queue = 0;
  48         for_each_possible_cpu(i) {
  49                 if (!cpu_online(i)) {
  50                         map[i] = 0;
  51                         continue;
  52                 }
  53
  54                 /*
  55                  * Easy case - we have equal or more hardware queues. Or
  56                  * there are no thread siblings to take into account. Do
  57                  * 1:1 if enough, or sequential mapping if less.
  58                  */
  59                 if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
  60                         map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
  61                         queue++;
  62                         continue;
  63                 }
  64
  65                 /*
  66                  * Less then nr_cpus queues, and we have some number of
  67                  * threads per cores. Map sibling threads to the same
  68                  * queue.
  69                  */
  70                 first_sibling = get_first_sibling(i);
  71                 if (first_sibling == i) {
  72                         map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
  73                                                         queue);
  74                         queue++;
  75                 } else
  76                         map[i] = map[first_sibling];
  77         }
  78
  79         free_cpumask_var(cpus);
  80         return 0;
  81 }
  82
  83 unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
  84 {
  85         unsigned int *map;
  86
  87         /* If cpus are offline, map them to first hctx */
  88         map = kzalloc_node(sizeof(*map) * num_possible_cpus(), GFP_KERNEL,
  89                                 set->numa_node);
  90         if (!map)
  91                 return NULL;
  92
  93         if (!blk_mq_update_queue_map(map, set->nr_hw_queues))
  94                 return map;
  95
  96         kfree(map);
  97         return NULL;
  98 }