95 lines
2.2 KiB
C
95 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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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 queue_index(struct blk_mq_queue_map *qmap,
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unsigned int nr_queues, const int q)
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{
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return qmap->queue_offset + (q % 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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void blk_mq_map_queues(struct blk_mq_queue_map *qmap)
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{
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unsigned int *map = qmap->mq_map;
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unsigned int nr_queues = qmap->nr_queues;
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unsigned int cpu, first_sibling, q = 0;
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for_each_possible_cpu(cpu)
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map[cpu] = -1;
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/*
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* Spread queues among present CPUs first for minimizing
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* count of dead queues which are mapped by all un-present CPUs
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*/
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for_each_present_cpu(cpu) {
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if (q >= nr_queues)
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break;
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map[cpu] = queue_index(qmap, nr_queues, q++);
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}
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for_each_possible_cpu(cpu) {
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if (map[cpu] != -1)
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continue;
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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
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* for performance optimizations.
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*/
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if (q < nr_queues) {
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map[cpu] = queue_index(qmap, nr_queues, q++);
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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] = queue_index(qmap, nr_queues, q++);
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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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}
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EXPORT_SYMBOL_GPL(blk_mq_map_queues);
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/**
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* blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
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* @qmap: CPU to hardware queue map.
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* @index: hardware queue index.
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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(struct blk_mq_queue_map *qmap, 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 == qmap->mq_map[i])
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return cpu_to_node(i);
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}
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return NUMA_NO_NODE;
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}
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