projects/linux·blob v3.0-rc1 · refs

269 lines · 6.8 KiB

1/*
2 * cpu_rmap.c: CPU affinity reverse-map support
3 * Copyright 2011 Solarflare Communications Inc.
4 *
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.
8 */
9
10#include <linux/cpu_rmap.h>
11#ifdef CONFIG_GENERIC_HARDIRQS
12#include <linux/interrupt.h>
13#endif
14#include <linux/module.h>
15
16/*
17 * These functions maintain a mapping from CPUs to some ordered set of
18 * objects with CPU affinities. This can be seen as a reverse-map of
19 * CPU affinity. However, we do not assume that the object affinities
20 * cover all CPUs in the system. For those CPUs not directly covered
21 * by object affinities, we attempt to find a nearest object based on
22 * CPU topology.
23 */
24
25/**
26 * alloc_cpu_rmap - allocate CPU affinity reverse-map
27 * @size: Number of objects to be mapped
28 * @flags: Allocation flags e.g. %GFP_KERNEL
29 */
30struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
31{
32 struct cpu_rmap *rmap;
33 unsigned int cpu;
34 size_t obj_offset;
35
36 /* This is a silly number of objects, and we use u16 indices. */
37 if (size > 0xffff)
38 return NULL;
39
40 /* Offset of object pointer array from base structure */
41 obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),
42 sizeof(void *));
43
44 rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);
45 if (!rmap)
46 return NULL;
47
48 rmap->obj = (void **)((char *)rmap + obj_offset);
49
50 /* Initially assign CPUs to objects on a rota, since we have
51 * no idea where the objects are. Use infinite distance, so
52 * any object with known distance is preferable. Include the
53 * CPUs that are not present/online, since we definitely want
54 * any newly-hotplugged CPUs to have some object assigned.
55 */
56 for_each_possible_cpu(cpu) {
57 rmap->near[cpu].index = cpu % size;
58 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
59 }
60
61 rmap->size = size;
62 return rmap;
63}
64EXPORT_SYMBOL(alloc_cpu_rmap);
65
66/* Reevaluate nearest object for given CPU, comparing with the given
67 * neighbours at the given distance.
68 */
69static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
70 const struct cpumask *mask, u16 dist)
71{
72 int neigh;
73
74 for_each_cpu(neigh, mask) {
75 if (rmap->near[cpu].dist > dist &&
76 rmap->near[neigh].dist <= dist) {
77 rmap->near[cpu].index = rmap->near[neigh].index;
78 rmap->near[cpu].dist = dist;
79 return true;
80 }
81 }
82 return false;
83}
84
85#ifdef DEBUG
86static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
87{
88 unsigned index;
89 unsigned int cpu;
90
91 pr_info("cpu_rmap %p, %s:\n", rmap, prefix);
92
93 for_each_possible_cpu(cpu) {
94 index = rmap->near[cpu].index;
95 pr_info("cpu %d -> obj %u (distance %u)\n",
96 cpu, index, rmap->near[cpu].dist);
97 }
98}
99#else
100static inline void
101debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
102{
103}
104#endif
105
106/**
107 * cpu_rmap_add - add object to a rmap
108 * @rmap: CPU rmap allocated with alloc_cpu_rmap()
109 * @obj: Object to add to rmap
110 *
111 * Return index of object.
112 */
113int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
114{
115 u16 index;
116
117 BUG_ON(rmap->used >= rmap->size);
118 index = rmap->used++;
119 rmap->obj[index] = obj;
120 return index;
121}
122EXPORT_SYMBOL(cpu_rmap_add);
123
124/**
125 * cpu_rmap_update - update CPU rmap following a change of object affinity
126 * @rmap: CPU rmap to update
127 * @index: Index of object whose affinity changed
128 * @affinity: New CPU affinity of object
129 */
130int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
131 const struct cpumask *affinity)
132{
133 cpumask_var_t update_mask;
134 unsigned int cpu;
135
136 if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
137 return -ENOMEM;
138
139 /* Invalidate distance for all CPUs for which this used to be
140 * the nearest object. Mark those CPUs for update.
141 */
142 for_each_online_cpu(cpu) {
143 if (rmap->near[cpu].index == index) {
144 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
145 cpumask_set_cpu(cpu, update_mask);
146 }
147 }
148
149 debug_print_rmap(rmap, "after invalidating old distances");
150
151 /* Set distance to 0 for all CPUs in the new affinity mask.
152 * Mark all CPUs within their NUMA nodes for update.
153 */
154 for_each_cpu(cpu, affinity) {
155 rmap->near[cpu].index = index;
156 rmap->near[cpu].dist = 0;
157 cpumask_or(update_mask, update_mask,
158 cpumask_of_node(cpu_to_node(cpu)));
159 }
160
161 debug_print_rmap(rmap, "after updating neighbours");
162
163 /* Update distances based on topology */
164 for_each_cpu(cpu, update_mask) {
165 if (cpu_rmap_copy_neigh(rmap, cpu,
166 topology_thread_cpumask(cpu), 1))
167 continue;
168 if (cpu_rmap_copy_neigh(rmap, cpu,
169 topology_core_cpumask(cpu), 2))
170 continue;
171 if (cpu_rmap_copy_neigh(rmap, cpu,
172 cpumask_of_node(cpu_to_node(cpu)), 3))
173 continue;
174 /* We could continue into NUMA node distances, but for now
175 * we give up.
176 */
177 }
178
179 debug_print_rmap(rmap, "after copying neighbours");
180
181 free_cpumask_var(update_mask);
182 return 0;
183}
184EXPORT_SYMBOL(cpu_rmap_update);
185
186#ifdef CONFIG_GENERIC_HARDIRQS
187
188/* Glue between IRQ affinity notifiers and CPU rmaps */
189
190struct irq_glue {
191 struct irq_affinity_notify notify;
192 struct cpu_rmap *rmap;
193 u16 index;
194};
195
196/**
197 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
198 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
199 *
200 * Must be called in process context, before freeing the IRQs, and
201 * without holding any locks required by global workqueue items.
202 */
203void free_irq_cpu_rmap(struct cpu_rmap *rmap)
204{
205 struct irq_glue *glue;
206 u16 index;
207
208 if (!rmap)
209 return;
210
211 for (index = 0; index < rmap->used; index++) {
212 glue = rmap->obj[index];
213 irq_set_affinity_notifier(glue->notify.irq, NULL);
214 }
215 irq_run_affinity_notifiers();
216
217 kfree(rmap);
218}
219EXPORT_SYMBOL(free_irq_cpu_rmap);
220
221static void
222irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
223{
224 struct irq_glue *glue =
225 container_of(notify, struct irq_glue, notify);
226 int rc;
227
228 rc = cpu_rmap_update(glue->rmap, glue->index, mask);
229 if (rc)
230 pr_warning("irq_cpu_rmap_notify: update failed: %d\n", rc);
231}
232
233static void irq_cpu_rmap_release(struct kref *ref)
234{
235 struct irq_glue *glue =
236 container_of(ref, struct irq_glue, notify.kref);
237 kfree(glue);
238}
239
240/**
241 * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
242 * @rmap: The reverse-map
243 * @irq: The IRQ number
244 *
245 * This adds an IRQ affinity notifier that will update the reverse-map
246 * automatically.
247 *
248 * Must be called in process context, after the IRQ is allocated but
249 * before it is bound with request_irq().
250 */
251int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
252{
253 struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
254 int rc;
255
256 if (!glue)
257 return -ENOMEM;
258 glue->notify.notify = irq_cpu_rmap_notify;
259 glue->notify.release = irq_cpu_rmap_release;
260 glue->rmap = rmap;
261 glue->index = cpu_rmap_add(rmap, glue);
262 rc = irq_set_affinity_notifier(irq, &glue->notify);
263 if (rc)
264 kfree(glue);
265 return rc;
266}
267EXPORT_SYMBOL(irq_cpu_rmap_add);
268
269#endif /* CONFIG_GENERIC_HARDIRQS */