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-rw-r--r--block/blk-mq-cpumap.c108
1 files changed, 108 insertions, 0 deletions
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
new file mode 100644
index 00000000000..f8721278601
--- /dev/null
+++ b/block/blk-mq-cpumap.c
@@ -0,0 +1,108 @@
+#include <linux/kernel.h>
+#include <linux/threads.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/cpu.h>
+
+#include <linux/blk-mq.h>
+#include "blk.h"
+#include "blk-mq.h"
+
+static void show_map(unsigned int *map, unsigned int nr)
+{
+ int i;
+
+ pr_info("blk-mq: CPU -> queue map\n");
+ for_each_online_cpu(i)
+ pr_info(" CPU%2u -> Queue %u\n", i, map[i]);
+}
+
+static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
+ const int cpu)
+{
+ return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
+}
+
+static int get_first_sibling(unsigned int cpu)
+{
+ unsigned int ret;
+
+ ret = cpumask_first(topology_thread_cpumask(cpu));
+ if (ret < nr_cpu_ids)
+ return ret;
+
+ return cpu;
+}
+
+int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
+{
+ unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
+ cpumask_var_t cpus;
+
+ if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
+ return 1;
+
+ cpumask_clear(cpus);
+ nr_cpus = nr_uniq_cpus = 0;
+ for_each_online_cpu(i) {
+ 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 (!cpu_online(i)) {
+ map[i] = 0;
+ continue;
+ }
+
+ /*
+ * 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.
+ */
+ if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
+ map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
+ queue++;
+ continue;
+ }
+
+ /*
+ * 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];
+ }
+
+ show_map(map, nr_cpus);
+ free_cpumask_var(cpus);
+ return 0;
+}
+
+unsigned int *blk_mq_make_queue_map(struct blk_mq_reg *reg)
+{
+ unsigned int *map;
+
+ /* If cpus are offline, map them to first hctx */
+ map = kzalloc_node(sizeof(*map) * num_possible_cpus(), GFP_KERNEL,
+ reg->numa_node);
+ if (!map)
+ return NULL;
+
+ if (!blk_mq_update_queue_map(map, reg->nr_hw_queues))
+ return map;
+
+ kfree(map);
+ return NULL;
+}