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-rw-r--r--block/blk-mq-cpumap.c68
1 files changed, 21 insertions, 47 deletions
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 8e61e8640e17..4891f042a22f 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -14,10 +14,14 @@
#include "blk.h"
#include "blk-mq.h"
-static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
- const int cpu)
+static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
{
- return cpu * nr_queues / nr_cpus;
+ /*
+ * Non online CPU will be mapped to queue index 0.
+ */
+ if (!cpu_online(cpu))
+ return 0;
+ return cpu % nr_queues;
}
static int get_first_sibling(unsigned int cpu)
@@ -35,56 +39,26 @@ int blk_mq_map_queues(struct blk_mq_tag_set *set)
{
unsigned int *map = set->mq_map;
unsigned int nr_queues = set->nr_hw_queues;
- const struct cpumask *online_mask = cpu_online_mask;
- unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
- cpumask_var_t cpus;
-
- if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
- return -ENOMEM;
-
- cpumask_clear(cpus);
- nr_cpus = nr_uniq_cpus = 0;
- for_each_cpu(i, online_mask) {
- nr_cpus++;
- first_sibling = get_first_sibling(i);
- if (!cpumask_test_cpu(first_sibling, cpus))
- nr_uniq_cpus++;
- cpumask_set_cpu(i, cpus);
- }
-
- queue = 0;
- for_each_possible_cpu(i) {
- if (!cpumask_test_cpu(i, online_mask)) {
- map[i] = 0;
- continue;
- }
+ unsigned int cpu, first_sibling;
+ for_each_possible_cpu(cpu) {
/*
- * Easy case - we have equal or more hardware queues. Or
- * there are no thread siblings to take into account. Do
- * 1:1 if enough, or sequential mapping if less.
+ * First do sequential mapping between CPUs and queues.
+ * In case we still have CPUs to map, and we have some number of
+ * threads per cores then map sibling threads to the same queue for
+ * performace optimizations.
*/
- if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
- map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
- queue++;
- continue;
+ if (cpu < nr_queues) {
+ map[cpu] = cpu_to_queue_index(nr_queues, cpu);
+ } else {
+ first_sibling = get_first_sibling(cpu);
+ if (first_sibling == cpu)
+ map[cpu] = cpu_to_queue_index(nr_queues, cpu);
+ else
+ map[cpu] = map[first_sibling];
}
-
- /*
- * Less then nr_cpus queues, and we have some number of
- * threads per cores. Map sibling threads to the same
- * queue.
- */
- first_sibling = get_first_sibling(i);
- if (first_sibling == i) {
- map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
- queue);
- queue++;
- } else
- map[i] = map[first_sibling];
}
- free_cpumask_var(cpus);
return 0;
}
EXPORT_SYMBOL_GPL(blk_mq_map_queues);