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Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -07001/*
2 * Fast batching percpu counters.
3 */
4
5#include <linux/percpu_counter.h>
Andrew Mortonc67ad912007-07-15 23:39:51 -07006#include <linux/notifier.h>
7#include <linux/mutex.h>
8#include <linux/init.h>
9#include <linux/cpu.h>
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070010#include <linux/module.h>
Tejun Heoe2852ae2010-10-26 14:23:05 -070011#include <linux/debugobjects.h>
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070012
Andrew Mortonc67ad912007-07-15 23:39:51 -070013static LIST_HEAD(percpu_counters);
14static DEFINE_MUTEX(percpu_counters_lock);
Andrew Mortonc67ad912007-07-15 23:39:51 -070015
Tejun Heoe2852ae2010-10-26 14:23:05 -070016#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
Peter Zijlstra3a587f42007-10-16 23:25:44 -070058void 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
Peter Zijlstra20e89762007-10-16 23:25:43 -070072void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070073{
Peter Zijlstra20e89762007-10-16 23:25:43 -070074 s64 count;
Mingming Cao0216bfc2006-06-23 02:05:41 -070075 s32 *pcount;
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070076
Christoph Lameterea00c302010-10-26 14:23:09 -070077 preempt_disable();
78 pcount = this_cpu_ptr(fbc->counters);
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070079 count = *pcount + amount;
Peter Zijlstra252e0ba2007-10-16 23:25:43 -070080 if (count >= batch || count <= -batch) {
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070081 spin_lock(&fbc->lock);
82 fbc->count += count;
83 *pcount = 0;
84 spin_unlock(&fbc->lock);
85 } else {
86 *pcount = count;
87 }
Christoph Lameterea00c302010-10-26 14:23:09 -070088 preempt_enable();
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070089}
Peter Zijlstra252e0ba2007-10-16 23:25:43 -070090EXPORT_SYMBOL(__percpu_counter_add);
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070091
92/*
93 * Add up all the per-cpu counts, return the result. This is a more accurate
94 * but much slower version of percpu_counter_read_positive()
95 */
Andrew Morton02d21162008-12-09 13:14:14 -080096s64 __percpu_counter_sum(struct percpu_counter *fbc)
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070097{
Mingming Cao0216bfc2006-06-23 02:05:41 -070098 s64 ret;
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070099 int cpu;
100
101 spin_lock(&fbc->lock);
102 ret = fbc->count;
Andrew Mortonb4ef0292007-07-15 23:39:51 -0700103 for_each_online_cpu(cpu) {
Mingming Cao0216bfc2006-06-23 02:05:41 -0700104 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -0700105 ret += *pcount;
106 }
107 spin_unlock(&fbc->lock);
Peter Zijlstrabf1d89c2007-10-16 23:25:45 -0700108 return ret;
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -0700109}
Peter Zijlstrabf1d89c2007-10-16 23:25:45 -0700110EXPORT_SYMBOL(__percpu_counter_sum);
Andrew Mortonc67ad912007-07-15 23:39:51 -0700111
Peter Zijlstraea319512008-12-26 15:08:55 +0100112int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
113 struct lock_class_key *key)
Andrew Mortonc67ad912007-07-15 23:39:51 -0700114{
115 spin_lock_init(&fbc->lock);
Peter Zijlstraea319512008-12-26 15:08:55 +0100116 lockdep_set_class(&fbc->lock, key);
Andrew Mortonc67ad912007-07-15 23:39:51 -0700117 fbc->count = amount;
118 fbc->counters = alloc_percpu(s32);
Peter Zijlstra833f4072007-10-16 23:25:45 -0700119 if (!fbc->counters)
120 return -ENOMEM;
Tejun Heoe2852ae2010-10-26 14:23:05 -0700121
122 debug_percpu_counter_activate(fbc);
123
Andrew Mortonc67ad912007-07-15 23:39:51 -0700124#ifdef CONFIG_HOTPLUG_CPU
Masanori ITOH8474b592010-10-26 14:21:20 -0700125 INIT_LIST_HEAD(&fbc->list);
Andrew Mortonc67ad912007-07-15 23:39:51 -0700126 mutex_lock(&percpu_counters_lock);
127 list_add(&fbc->list, &percpu_counters);
128 mutex_unlock(&percpu_counters_lock);
129#endif
Peter Zijlstra833f4072007-10-16 23:25:45 -0700130 return 0;
Andrew Mortonc67ad912007-07-15 23:39:51 -0700131}
Peter Zijlstraea319512008-12-26 15:08:55 +0100132EXPORT_SYMBOL(__percpu_counter_init);
Peter Zijlstradc62a302007-10-16 23:25:46 -0700133
Andrew Mortonc67ad912007-07-15 23:39:51 -0700134void percpu_counter_destroy(struct percpu_counter *fbc)
135{
Peter Zijlstra833f4072007-10-16 23:25:45 -0700136 if (!fbc->counters)
137 return;
138
Tejun Heoe2852ae2010-10-26 14:23:05 -0700139 debug_percpu_counter_deactivate(fbc);
140
Andrew Mortonc67ad912007-07-15 23:39:51 -0700141#ifdef CONFIG_HOTPLUG_CPU
142 mutex_lock(&percpu_counters_lock);
143 list_del(&fbc->list);
144 mutex_unlock(&percpu_counters_lock);
145#endif
Eric Dumazetfd3d6642008-12-09 13:14:11 -0800146 free_percpu(fbc->counters);
147 fbc->counters = NULL;
Andrew Mortonc67ad912007-07-15 23:39:51 -0700148}
149EXPORT_SYMBOL(percpu_counter_destroy);
150
Eric Dumazet179f7eb2009-01-06 14:41:04 -0800151int percpu_counter_batch __read_mostly = 32;
152EXPORT_SYMBOL(percpu_counter_batch);
153
154static void compute_batch_value(void)
155{
156 int nr = num_online_cpus();
157
158 percpu_counter_batch = max(32, nr*2);
159}
160
Andrew Mortonc67ad912007-07-15 23:39:51 -0700161static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
162 unsigned long action, void *hcpu)
163{
Eric Dumazet179f7eb2009-01-06 14:41:04 -0800164#ifdef CONFIG_HOTPLUG_CPU
Andrew Mortonc67ad912007-07-15 23:39:51 -0700165 unsigned int cpu;
166 struct percpu_counter *fbc;
167
Eric Dumazet179f7eb2009-01-06 14:41:04 -0800168 compute_batch_value();
Andrew Mortonc67ad912007-07-15 23:39:51 -0700169 if (action != CPU_DEAD)
170 return NOTIFY_OK;
171
172 cpu = (unsigned long)hcpu;
173 mutex_lock(&percpu_counters_lock);
174 list_for_each_entry(fbc, &percpu_counters, list) {
175 s32 *pcount;
Gautham R Shenoyd2b20b12007-10-18 23:40:47 -0700176 unsigned long flags;
Andrew Mortonc67ad912007-07-15 23:39:51 -0700177
Gautham R Shenoyd2b20b12007-10-18 23:40:47 -0700178 spin_lock_irqsave(&fbc->lock, flags);
Andrew Mortonc67ad912007-07-15 23:39:51 -0700179 pcount = per_cpu_ptr(fbc->counters, cpu);
180 fbc->count += *pcount;
181 *pcount = 0;
Gautham R Shenoyd2b20b12007-10-18 23:40:47 -0700182 spin_unlock_irqrestore(&fbc->lock, flags);
Andrew Mortonc67ad912007-07-15 23:39:51 -0700183 }
184 mutex_unlock(&percpu_counters_lock);
Eric Dumazet179f7eb2009-01-06 14:41:04 -0800185#endif
Andrew Mortonc67ad912007-07-15 23:39:51 -0700186 return NOTIFY_OK;
187}
188
Tim Chen27f5e0f2010-08-09 17:19:04 -0700189/*
190 * Compare counter against given value.
191 * Return 1 if greater, 0 if equal and -1 if less
192 */
193int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
194{
195 s64 count;
196
197 count = percpu_counter_read(fbc);
198 /* Check to see if rough count will be sufficient for comparison */
199 if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) {
200 if (count > rhs)
201 return 1;
202 else
203 return -1;
204 }
205 /* Need to use precise count */
206 count = percpu_counter_sum(fbc);
207 if (count > rhs)
208 return 1;
209 else if (count < rhs)
210 return -1;
211 else
212 return 0;
213}
214EXPORT_SYMBOL(percpu_counter_compare);
215
Andrew Mortonc67ad912007-07-15 23:39:51 -0700216static int __init percpu_counter_startup(void)
217{
Eric Dumazet179f7eb2009-01-06 14:41:04 -0800218 compute_batch_value();
Andrew Mortonc67ad912007-07-15 23:39:51 -0700219 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
220 return 0;
221}
222module_init(percpu_counter_startup);