linux/lib/group_cpus.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016 Thomas Gleixner.
 * Copyright (C) 2016-2017 Christoph Hellwig.
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/sort.h>
#include <linux/group_cpus.h>

#ifdef CONFIG_SMP

static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
				unsigned int cpus_per_grp)
{ … }

static cpumask_var_t *alloc_node_to_cpumask(void)
{ … }

static void free_node_to_cpumask(cpumask_var_t *masks)
{ … }

static void build_node_to_cpumask(cpumask_var_t *masks)
{ … }

static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
				const struct cpumask *mask, nodemask_t *nodemsk)
{ … }

struct node_groups { … };

static int ncpus_cmp_func(const void *l, const void *r)
{ … }

/*
 * Allocate group number for each node, so that for each node:
 *
 * 1) the allocated number is >= 1
 *
 * 2) the allocated number is <= active CPU number of this node
 *
 * The actual allocated total groups may be less than @numgrps when
 * active total CPU number is less than @numgrps.
 *
 * Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
 * for each node.
 */
static void alloc_nodes_groups(unsigned int numgrps,
			       cpumask_var_t *node_to_cpumask,
			       const struct cpumask *cpu_mask,
			       const nodemask_t nodemsk,
			       struct cpumask *nmsk,
			       struct node_groups *node_groups)
{ … }

static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
			       cpumask_var_t *node_to_cpumask,
			       const struct cpumask *cpu_mask,
			       struct cpumask *nmsk, struct cpumask *masks)
{ … }

/**
 * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
 * @numgrps: number of groups
 *
 * Return: cpumask array if successful, NULL otherwise. And each element
 * includes CPUs assigned to this group
 *
 * Try to put close CPUs from viewpoint of CPU and NUMA locality into
 * same group, and run two-stage grouping:
 *	1) allocate present CPUs on these groups evenly first
 *	2) allocate other possible CPUs on these groups evenly
 *
 * We guarantee in the resulted grouping that all CPUs are covered, and
 * no same CPU is assigned to multiple groups
 */
struct cpumask *group_cpus_evenly(unsigned int numgrps)
{ … }
#else /* CONFIG_SMP */
struct cpumask *group_cpus_evenly(unsigned int numgrps)
{
	struct cpumask *masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL);

	if (!masks)
		return NULL;

	/* assign all CPUs(cpu 0) to the 1st group only */
	cpumask_copy(&masks[0], cpu_possible_mask);
	return masks;
}
#endif /* CONFIG_SMP */
EXPORT_SYMBOL_GPL(…);