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1/*
2 * Fast batching percpu counters.
3 */
4
5#include <linux/percpu_counter.h>
6#include <linux/notifier.h>
7#include <linux/mutex.h>
8#include <linux/init.h>
9#include <linux/cpu.h>
10#include <linux/module.h>
11#include <linux/debugobjects.h>
12
13#ifdef CONFIG_HOTPLUG_CPU
14static LIST_HEAD(percpu_counters);
15static DEFINE_SPINLOCK(percpu_counters_lock);
16#endif
17
18#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
19
20static struct debug_obj_descr percpu_counter_debug_descr;
21
22static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state)
23{
24 struct percpu_counter *fbc = addr;
25
26 switch (state) {
27 case ODEBUG_STATE_ACTIVE:
28 percpu_counter_destroy(fbc);
29 debug_object_free(fbc, &percpu_counter_debug_descr);
30 return 1;
31 default:
32 return 0;
33 }
34}
35
36static struct debug_obj_descr percpu_counter_debug_descr = {
37 .name = "percpu_counter",
38 .fixup_free = percpu_counter_fixup_free,
39};
40
41static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
42{
43 debug_object_init(fbc, &percpu_counter_debug_descr);
44 debug_object_activate(fbc, &percpu_counter_debug_descr);
45}
46
47static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
48{
49 debug_object_deactivate(fbc, &percpu_counter_debug_descr);
50 debug_object_free(fbc, &percpu_counter_debug_descr);
51}
52
53#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
54static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
55{ }
56static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
57{ }
58#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
59
60void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
61{
62 int cpu;
63 unsigned long flags;
64
65 raw_spin_lock_irqsave(&fbc->lock, flags);
66 for_each_possible_cpu(cpu) {
67 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
68 *pcount = 0;
69 }
70 fbc->count = amount;
71 raw_spin_unlock_irqrestore(&fbc->lock, flags);
72}
73EXPORT_SYMBOL(percpu_counter_set);
74
75void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
76{
77 s64 count;
78
79 preempt_disable();
80 count = __this_cpu_read(*fbc->counters) + amount;
81 if (count >= batch || count <= -batch) {
82 unsigned long flags;
83 raw_spin_lock_irqsave(&fbc->lock, flags);
84 fbc->count += count;
85 __this_cpu_sub(*fbc->counters, count - amount);
86 raw_spin_unlock_irqrestore(&fbc->lock, flags);
87 } else {
88 this_cpu_add(*fbc->counters, amount);
89 }
90 preempt_enable();
91}
92EXPORT_SYMBOL(__percpu_counter_add);
93
94/*
95 * Add up all the per-cpu counts, return the result. This is a more accurate
96 * but much slower version of percpu_counter_read_positive()
97 */
98s64 __percpu_counter_sum(struct percpu_counter *fbc)
99{
100 s64 ret;
101 int cpu;
102 unsigned long flags;
103
104 raw_spin_lock_irqsave(&fbc->lock, flags);
105 ret = fbc->count;
106 for_each_online_cpu(cpu) {
107 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
108 ret += *pcount;
109 }
110 raw_spin_unlock_irqrestore(&fbc->lock, flags);
111 return ret;
112}
113EXPORT_SYMBOL(__percpu_counter_sum);
114
115int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
116 struct lock_class_key *key)
117{
118 raw_spin_lock_init(&fbc->lock);
119 lockdep_set_class(&fbc->lock, key);
120 fbc->count = amount;
121 fbc->counters = alloc_percpu(s32);
122 if (!fbc->counters)
123 return -ENOMEM;
124
125 debug_percpu_counter_activate(fbc);
126
127#ifdef CONFIG_HOTPLUG_CPU
128 INIT_LIST_HEAD(&fbc->list);
129 spin_lock(&percpu_counters_lock);
130 list_add(&fbc->list, &percpu_counters);
131 spin_unlock(&percpu_counters_lock);
132#endif
133 return 0;
134}
135EXPORT_SYMBOL(__percpu_counter_init);
136
137void percpu_counter_destroy(struct percpu_counter *fbc)
138{
139 if (!fbc->counters)
140 return;
141
142 debug_percpu_counter_deactivate(fbc);
143
144#ifdef CONFIG_HOTPLUG_CPU
145 spin_lock(&percpu_counters_lock);
146 list_del(&fbc->list);
147 spin_unlock(&percpu_counters_lock);
148#endif
149 free_percpu(fbc->counters);
150 fbc->counters = NULL;
151}
152EXPORT_SYMBOL(percpu_counter_destroy);
153
154int percpu_counter_batch __read_mostly = 32;
155EXPORT_SYMBOL(percpu_counter_batch);
156
157static void compute_batch_value(void)
158{
159 int nr = num_online_cpus();
160
161 percpu_counter_batch = max(32, nr*2);
162}
163
164static int percpu_counter_hotcpu_callback(struct notifier_block *nb,
165 unsigned long action, void *hcpu)
166{
167#ifdef CONFIG_HOTPLUG_CPU
168 unsigned int cpu;
169 struct percpu_counter *fbc;
170
171 compute_batch_value();
172 if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
173 return NOTIFY_OK;
174
175 cpu = (unsigned long)hcpu;
176 spin_lock(&percpu_counters_lock);
177 list_for_each_entry(fbc, &percpu_counters, list) {
178 s32 *pcount;
179 unsigned long flags;
180
181 raw_spin_lock_irqsave(&fbc->lock, flags);
182 pcount = per_cpu_ptr(fbc->counters, cpu);
183 fbc->count += *pcount;
184 *pcount = 0;
185 raw_spin_unlock_irqrestore(&fbc->lock, flags);
186 }
187 spin_unlock(&percpu_counters_lock);
188#endif
189 return NOTIFY_OK;
190}
191
192/*
193 * Compare counter against given value.
194 * Return 1 if greater, 0 if equal and -1 if less
195 */
196int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
197{
198 s64 count;
199
200 count = percpu_counter_read(fbc);
201 /* Check to see if rough count will be sufficient for comparison */
202 if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) {
203 if (count > rhs)
204 return 1;
205 else
206 return -1;
207 }
208 /* Need to use precise count */
209 count = percpu_counter_sum(fbc);
210 if (count > rhs)
211 return 1;
212 else if (count < rhs)
213 return -1;
214 else
215 return 0;
216}
217EXPORT_SYMBOL(percpu_counter_compare);
218
219static int __init percpu_counter_startup(void)
220{
221 compute_batch_value();
222 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
223 return 0;
224}
225module_init(percpu_counter_startup);
1/*
2 * Fast batching percpu counters.
3 */
4
5#include <linux/percpu_counter.h>
6#include <linux/notifier.h>
7#include <linux/mutex.h>
8#include <linux/init.h>
9#include <linux/cpu.h>
10#include <linux/module.h>
11#include <linux/debugobjects.h>
12
13static LIST_HEAD(percpu_counters);
14static DEFINE_MUTEX(percpu_counters_lock);
15
16#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
17
18static struct debug_obj_descr percpu_counter_debug_descr;
19
20static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state)
21{
22 struct percpu_counter *fbc = addr;
23
24 switch (state) {
25 case ODEBUG_STATE_ACTIVE:
26 percpu_counter_destroy(fbc);
27 debug_object_free(fbc, &percpu_counter_debug_descr);
28 return 1;
29 default:
30 return 0;
31 }
32}
33
34static struct debug_obj_descr percpu_counter_debug_descr = {
35 .name = "percpu_counter",
36 .fixup_free = percpu_counter_fixup_free,
37};
38
39static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
40{
41 debug_object_init(fbc, &percpu_counter_debug_descr);
42 debug_object_activate(fbc, &percpu_counter_debug_descr);
43}
44
45static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
46{
47 debug_object_deactivate(fbc, &percpu_counter_debug_descr);
48 debug_object_free(fbc, &percpu_counter_debug_descr);
49}
50
51#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
52static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
53{ }
54static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
55{ }
56#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
57
58void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
59{
60 int cpu;
61
62 spin_lock(&fbc->lock);
63 for_each_possible_cpu(cpu) {
64 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
65 *pcount = 0;
66 }
67 fbc->count = amount;
68 spin_unlock(&fbc->lock);
69}
70EXPORT_SYMBOL(percpu_counter_set);
71
72void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
73{
74 s64 count;
75
76 preempt_disable();
77 count = __this_cpu_read(*fbc->counters) + amount;
78 if (count >= batch || count <= -batch) {
79 spin_lock(&fbc->lock);
80 fbc->count += count;
81 __this_cpu_write(*fbc->counters, 0);
82 spin_unlock(&fbc->lock);
83 } else {
84 __this_cpu_write(*fbc->counters, count);
85 }
86 preempt_enable();
87}
88EXPORT_SYMBOL(__percpu_counter_add);
89
90/*
91 * Add up all the per-cpu counts, return the result. This is a more accurate
92 * but much slower version of percpu_counter_read_positive()
93 */
94s64 __percpu_counter_sum(struct percpu_counter *fbc)
95{
96 s64 ret;
97 int cpu;
98
99 spin_lock(&fbc->lock);
100 ret = fbc->count;
101 for_each_online_cpu(cpu) {
102 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
103 ret += *pcount;
104 }
105 spin_unlock(&fbc->lock);
106 return ret;
107}
108EXPORT_SYMBOL(__percpu_counter_sum);
109
110int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
111 struct lock_class_key *key)
112{
113 spin_lock_init(&fbc->lock);
114 lockdep_set_class(&fbc->lock, key);
115 fbc->count = amount;
116 fbc->counters = alloc_percpu(s32);
117 if (!fbc->counters)
118 return -ENOMEM;
119
120 debug_percpu_counter_activate(fbc);
121
122#ifdef CONFIG_HOTPLUG_CPU
123 INIT_LIST_HEAD(&fbc->list);
124 mutex_lock(&percpu_counters_lock);
125 list_add(&fbc->list, &percpu_counters);
126 mutex_unlock(&percpu_counters_lock);
127#endif
128 return 0;
129}
130EXPORT_SYMBOL(__percpu_counter_init);
131
132void percpu_counter_destroy(struct percpu_counter *fbc)
133{
134 if (!fbc->counters)
135 return;
136
137 debug_percpu_counter_deactivate(fbc);
138
139#ifdef CONFIG_HOTPLUG_CPU
140 mutex_lock(&percpu_counters_lock);
141 list_del(&fbc->list);
142 mutex_unlock(&percpu_counters_lock);
143#endif
144 free_percpu(fbc->counters);
145 fbc->counters = NULL;
146}
147EXPORT_SYMBOL(percpu_counter_destroy);
148
149int percpu_counter_batch __read_mostly = 32;
150EXPORT_SYMBOL(percpu_counter_batch);
151
152static void compute_batch_value(void)
153{
154 int nr = num_online_cpus();
155
156 percpu_counter_batch = max(32, nr*2);
157}
158
159static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
160 unsigned long action, void *hcpu)
161{
162#ifdef CONFIG_HOTPLUG_CPU
163 unsigned int cpu;
164 struct percpu_counter *fbc;
165
166 compute_batch_value();
167 if (action != CPU_DEAD)
168 return NOTIFY_OK;
169
170 cpu = (unsigned long)hcpu;
171 mutex_lock(&percpu_counters_lock);
172 list_for_each_entry(fbc, &percpu_counters, list) {
173 s32 *pcount;
174 unsigned long flags;
175
176 spin_lock_irqsave(&fbc->lock, flags);
177 pcount = per_cpu_ptr(fbc->counters, cpu);
178 fbc->count += *pcount;
179 *pcount = 0;
180 spin_unlock_irqrestore(&fbc->lock, flags);
181 }
182 mutex_unlock(&percpu_counters_lock);
183#endif
184 return NOTIFY_OK;
185}
186
187/*
188 * Compare counter against given value.
189 * Return 1 if greater, 0 if equal and -1 if less
190 */
191int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
192{
193 s64 count;
194
195 count = percpu_counter_read(fbc);
196 /* Check to see if rough count will be sufficient for comparison */
197 if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) {
198 if (count > rhs)
199 return 1;
200 else
201 return -1;
202 }
203 /* Need to use precise count */
204 count = percpu_counter_sum(fbc);
205 if (count > rhs)
206 return 1;
207 else if (count < rhs)
208 return -1;
209 else
210 return 0;
211}
212EXPORT_SYMBOL(percpu_counter_compare);
213
214static int __init percpu_counter_startup(void)
215{
216 compute_batch_value();
217 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
218 return 0;
219}
220module_init(percpu_counter_startup);