/*
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* CPU <-> hardware queue mapping helpers
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*
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* Copyright (C) 2013-2014 Jens Axboe
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*/
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#include <linux/kernel.h>
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#include <linux/threads.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/cpu.h>
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#include <linux/blk-mq.h>
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#include "blk.h"
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#include "blk-mq.h"
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static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
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{
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return cpu % nr_queues;
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}
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static int get_first_sibling(unsigned int cpu)
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{
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unsigned int ret;
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ret = cpumask_first(topology_sibling_cpumask(cpu));
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if (ret < nr_cpu_ids)
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return ret;
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return cpu;
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}
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int blk_mq_map_queues(struct blk_mq_tag_set *set)
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{
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unsigned int *map = set->mq_map;
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unsigned int nr_queues = set->nr_hw_queues;
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unsigned int cpu, first_sibling;
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for_each_possible_cpu(cpu) {
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/*
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* First do sequential mapping between CPUs and queues.
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* In case we still have CPUs to map, and we have some number of
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* threads per cores then map sibling threads to the same queue for
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* performace optimizations.
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*/
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if (cpu < nr_queues) {
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map[cpu] = cpu_to_queue_index(nr_queues, cpu);
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} else {
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first_sibling = get_first_sibling(cpu);
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if (first_sibling == cpu)
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map[cpu] = cpu_to_queue_index(nr_queues, cpu);
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else
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map[cpu] = map[first_sibling];
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}
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(blk_mq_map_queues);
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/*
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* We have no quick way of doing reverse lookups. This is only used at
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* queue init time, so runtime isn't important.
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*/
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int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
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{
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int i;
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for_each_possible_cpu(i) {
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if (index == mq_map[i])
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return local_memory_node(cpu_to_node(i));
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}
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return NUMA_NO_NODE;
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}
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