2 * cpu_rmap.c: CPU affinity reverse-map support
3 * Copyright 2011 Solarflare Communications Inc.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published
7 * by the Free Software Foundation, incorporated herein by reference.
10 #include <linux/cpu_rmap.h>
11 #include <linux/interrupt.h>
12 #include <linux/export.h>
15 * These functions maintain a mapping from CPUs to some ordered set of
16 * objects with CPU affinities. This can be seen as a reverse-map of
17 * CPU affinity. However, we do not assume that the object affinities
18 * cover all CPUs in the system. For those CPUs not directly covered
19 * by object affinities, we attempt to find a nearest object based on
24 * alloc_cpu_rmap - allocate CPU affinity reverse-map
25 * @size: Number of objects to be mapped
26 * @flags: Allocation flags e.g. %GFP_KERNEL
28 struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
30 struct cpu_rmap *rmap;
34 /* This is a silly number of objects, and we use u16 indices. */
38 /* Offset of object pointer array from base structure */
39 obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),
42 rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);
46 kref_init(&rmap->refcount);
47 rmap->obj = (void **)((char *)rmap + obj_offset);
49 /* Initially assign CPUs to objects on a rota, since we have
50 * no idea where the objects are. Use infinite distance, so
51 * any object with known distance is preferable. Include the
52 * CPUs that are not present/online, since we definitely want
53 * any newly-hotplugged CPUs to have some object assigned.
55 for_each_possible_cpu(cpu) {
56 rmap->near[cpu].index = cpu % size;
57 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
63 EXPORT_SYMBOL(alloc_cpu_rmap);
66 * cpu_rmap_release - internal reclaiming helper called from kref_put
67 * @ref: kref to struct cpu_rmap
69 static void cpu_rmap_release(struct kref *ref)
71 struct cpu_rmap *rmap = container_of(ref, struct cpu_rmap, refcount);
76 * cpu_rmap_get - internal helper to get new ref on a cpu_rmap
77 * @rmap: reverse-map allocated with alloc_cpu_rmap()
79 static inline void cpu_rmap_get(struct cpu_rmap *rmap)
81 kref_get(&rmap->refcount);
85 * cpu_rmap_put - release ref on a cpu_rmap
86 * @rmap: reverse-map allocated with alloc_cpu_rmap()
88 int cpu_rmap_put(struct cpu_rmap *rmap)
90 return kref_put(&rmap->refcount, cpu_rmap_release);
92 EXPORT_SYMBOL(cpu_rmap_put);
94 /* Reevaluate nearest object for given CPU, comparing with the given
95 * neighbours at the given distance.
97 static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
98 const struct cpumask *mask, u16 dist)
102 for_each_cpu(neigh, mask) {
103 if (rmap->near[cpu].dist > dist &&
104 rmap->near[neigh].dist <= dist) {
105 rmap->near[cpu].index = rmap->near[neigh].index;
106 rmap->near[cpu].dist = dist;
114 static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
119 pr_info("cpu_rmap %p, %s:\n", rmap, prefix);
121 for_each_possible_cpu(cpu) {
122 index = rmap->near[cpu].index;
123 pr_info("cpu %d -> obj %u (distance %u)\n",
124 cpu, index, rmap->near[cpu].dist);
129 debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
135 * cpu_rmap_add - add object to a rmap
136 * @rmap: CPU rmap allocated with alloc_cpu_rmap()
137 * @obj: Object to add to rmap
139 * Return index of object.
141 int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
145 BUG_ON(rmap->used >= rmap->size);
146 index = rmap->used++;
147 rmap->obj[index] = obj;
150 EXPORT_SYMBOL(cpu_rmap_add);
153 * cpu_rmap_update - update CPU rmap following a change of object affinity
154 * @rmap: CPU rmap to update
155 * @index: Index of object whose affinity changed
156 * @affinity: New CPU affinity of object
158 int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
159 const struct cpumask *affinity)
161 cpumask_var_t update_mask;
164 if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
167 /* Invalidate distance for all CPUs for which this used to be
168 * the nearest object. Mark those CPUs for update.
170 for_each_online_cpu(cpu) {
171 if (rmap->near[cpu].index == index) {
172 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
173 cpumask_set_cpu(cpu, update_mask);
177 debug_print_rmap(rmap, "after invalidating old distances");
179 /* Set distance to 0 for all CPUs in the new affinity mask.
180 * Mark all CPUs within their NUMA nodes for update.
182 for_each_cpu(cpu, affinity) {
183 rmap->near[cpu].index = index;
184 rmap->near[cpu].dist = 0;
185 cpumask_or(update_mask, update_mask,
186 cpumask_of_node(cpu_to_node(cpu)));
189 debug_print_rmap(rmap, "after updating neighbours");
191 /* Update distances based on topology */
192 for_each_cpu(cpu, update_mask) {
193 if (cpu_rmap_copy_neigh(rmap, cpu,
194 topology_thread_cpumask(cpu), 1))
196 if (cpu_rmap_copy_neigh(rmap, cpu,
197 topology_core_cpumask(cpu), 2))
199 if (cpu_rmap_copy_neigh(rmap, cpu,
200 cpumask_of_node(cpu_to_node(cpu)), 3))
202 /* We could continue into NUMA node distances, but for now
207 debug_print_rmap(rmap, "after copying neighbours");
209 free_cpumask_var(update_mask);
212 EXPORT_SYMBOL(cpu_rmap_update);
214 /* Glue between IRQ affinity notifiers and CPU rmaps */
217 struct irq_affinity_notify notify;
218 struct cpu_rmap *rmap;
223 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
224 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
226 * Must be called in process context, before freeing the IRQs.
228 void free_irq_cpu_rmap(struct cpu_rmap *rmap)
230 struct irq_glue *glue;
236 for (index = 0; index < rmap->used; index++) {
237 glue = rmap->obj[index];
238 irq_set_affinity_notifier(glue->notify.irq, NULL);
243 EXPORT_SYMBOL(free_irq_cpu_rmap);
246 * irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated
247 * @notify: struct irq_affinity_notify passed by irq/manage.c
248 * @mask: cpu mask for new SMP affinity
250 * This is executed in workqueue context.
253 irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
255 struct irq_glue *glue =
256 container_of(notify, struct irq_glue, notify);
259 rc = cpu_rmap_update(glue->rmap, glue->index, mask);
261 pr_warning("irq_cpu_rmap_notify: update failed: %d\n", rc);
265 * irq_cpu_rmap_release - reclaiming callback for IRQ subsystem
266 * @ref: kref to struct irq_affinity_notify passed by irq/manage.c
268 static void irq_cpu_rmap_release(struct kref *ref)
270 struct irq_glue *glue =
271 container_of(ref, struct irq_glue, notify.kref);
273 cpu_rmap_put(glue->rmap);
278 * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
279 * @rmap: The reverse-map
280 * @irq: The IRQ number
282 * This adds an IRQ affinity notifier that will update the reverse-map
285 * Must be called in process context, after the IRQ is allocated but
286 * before it is bound with request_irq().
288 int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
290 struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
295 glue->notify.notify = irq_cpu_rmap_notify;
296 glue->notify.release = irq_cpu_rmap_release;
299 glue->index = cpu_rmap_add(rmap, glue);
300 rc = irq_set_affinity_notifier(irq, &glue->notify);
302 cpu_rmap_put(glue->rmap);
307 EXPORT_SYMBOL(irq_cpu_rmap_add);