affinity.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2016 Thomas Gleixner.
  4 * Copyright (C) 2016-2017 Christoph Hellwig.
  5 */
  6#include <linux/interrupt.h>
  7#include <linux/kernel.h>
  8#include <linux/slab.h>
  9#include <linux/cpu.h>
 10#include <linux/group_cpus.h>
 11
 12static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
 13{
 14	affd->nr_sets = 1;
 15	affd->set_size[0] = affvecs;
 16}
 17
 18/**
 19 * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
 20 * @nvecs:	The total number of vectors
 21 * @affd:	Description of the affinity requirements
 22 *
 23 * Returns the irq_affinity_desc pointer or NULL if allocation failed.
 24 */
 25struct irq_affinity_desc *
 26irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
 27{
 28	unsigned int affvecs, curvec, usedvecs, i;
 29	struct irq_affinity_desc *masks = NULL;
 30
 31	/*
 32	 * Determine the number of vectors which need interrupt affinities
 33	 * assigned. If the pre/post request exhausts the available vectors
 34	 * then nothing to do here except for invoking the calc_sets()
 35	 * callback so the device driver can adjust to the situation.
 36	 */
 37	if (nvecs > affd->pre_vectors + affd->post_vectors)
 38		affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
 39	else
 40		affvecs = 0;
 41
 42	/*
 43	 * Simple invocations do not provide a calc_sets() callback. Install
 44	 * the generic one.
 45	 */
 46	if (!affd->calc_sets)
 47		affd->calc_sets = default_calc_sets;
 48
 49	/* Recalculate the sets */
 50	affd->calc_sets(affd, affvecs);
 51
 52	if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
 53		return NULL;
 54
 55	/* Nothing to assign? */
 56	if (!affvecs)
 57		return NULL;
 58
 59	masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
 60	if (!masks)
 61		return NULL;
 62
 63	/* Fill out vectors at the beginning that don't need affinity */
 64	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 65		cpumask_copy(&masks[curvec].mask, irq_default_affinity);
 66
 67	/*
 68	 * Spread on present CPUs starting from affd->pre_vectors. If we
 69	 * have multiple sets, build each sets affinity mask separately.
 70	 */
 71	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
 72		unsigned int nr_masks, this_vecs = affd->set_size[i];
 73		struct cpumask *result = group_cpus_evenly(this_vecs, &nr_masks);
 74
 75		if (!result) {
 76			kfree(masks);
 77			return NULL;
 78		}
 79
 80		for (int j = 0; j < nr_masks; j++)
 81			cpumask_copy(&masks[curvec + j].mask, &result[j]);
 82		kfree(result);
 83
 84		curvec += nr_masks;
 85		usedvecs += nr_masks;
 86	}
 87
 88	/* Fill out vectors at the end that don't need affinity */
 89	if (usedvecs >= affvecs)
 90		curvec = affd->pre_vectors + affvecs;
 91	else
 92		curvec = affd->pre_vectors + usedvecs;
 93	for (; curvec < nvecs; curvec++)
 94		cpumask_copy(&masks[curvec].mask, irq_default_affinity);
 95
 96	/* Mark the managed interrupts */
 97	for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
 98		masks[i].is_managed = 1;
 99
100	return masks;
101}
102
103/**
104 * irq_calc_affinity_vectors - Calculate the optimal number of vectors
105 * @minvec:	The minimum number of vectors available
106 * @maxvec:	The maximum number of vectors available
107 * @affd:	Description of the affinity requirements
108 */
109unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
110				       const struct irq_affinity *affd)
111{
112	unsigned int resv = affd->pre_vectors + affd->post_vectors;
113	unsigned int set_vecs;
114
115	if (resv > minvec)
116		return 0;
117
118	if (affd->calc_sets) {
119		set_vecs = maxvec - resv;
120	} else {
121		cpus_read_lock();
122		set_vecs = cpumask_weight(cpu_possible_mask);
123		cpus_read_unlock();
124	}
125
126	return resv + min(set_vecs, maxvec - resv);
127}