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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;
}
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