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-rw-r--r--block/blk-mq-cpumap.c96
1 files changed, 96 insertions, 0 deletions
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
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+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CPU <-> hardware queue mapping helpers
+ *
+ * Copyright (C) 2013-2014 Jens Axboe
+ */
+#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 int queue_index(struct blk_mq_queue_map *qmap,
+ unsigned int nr_queues, const int q)
+{
+ return qmap->queue_offset + (q % nr_queues);
+}
+
+static int get_first_sibling(unsigned int cpu)
+{
+ unsigned int ret;
+
+ ret = cpumask_first(topology_sibling_cpumask(cpu));
+ if (ret < nr_cpu_ids)
+ return ret;
+
+ return cpu;
+}
+
+int blk_mq_map_queues(struct blk_mq_queue_map *qmap)
+{
+ unsigned int *map = qmap->mq_map;
+ unsigned int nr_queues = qmap->nr_queues;
+ unsigned int cpu, first_sibling, q = 0;
+
+ for_each_possible_cpu(cpu)
+ map[cpu] = -1;
+
+ /*
+ * Spread queues among present CPUs first for minimizing
+ * count of dead queues which are mapped by all un-present CPUs
+ */
+ for_each_present_cpu(cpu) {
+ if (q >= nr_queues)
+ break;
+ map[cpu] = queue_index(qmap, nr_queues, q++);
+ }
+
+ for_each_possible_cpu(cpu) {
+ if (map[cpu] != -1)
+ continue;
+ /*
+ * 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 performance optimizations.
+ */
+ if (q < nr_queues) {
+ map[cpu] = queue_index(qmap, nr_queues, q++);
+ } else {
+ first_sibling = get_first_sibling(cpu);
+ if (first_sibling == cpu)
+ map[cpu] = queue_index(qmap, nr_queues, q++);
+ else
+ map[cpu] = map[first_sibling];
+ }
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(blk_mq_map_queues);
+
+/**
+ * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
+ * @qmap: CPU to hardware queue map.
+ * @index: hardware queue index.
+ *
+ * We have no quick way of doing reverse lookups. This is only used at
+ * queue init time, so runtime isn't important.
+ */
+int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ if (index == qmap->mq_map[i])
+ return cpu_to_node(i);
+ }
+
+ return NUMA_NO_NODE;
+}