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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>
11
Andrew Mortonc67ad912007-07-15 23:39:51 -070012#ifdef CONFIG_HOTPLUG_CPU
13static LIST_HEAD(percpu_counters);
14static DEFINE_MUTEX(percpu_counters_lock);
15#endif
16
Peter Zijlstra3a587f42007-10-16 23:25:44 -070017void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
18{
19 int cpu;
20
21 spin_lock(&fbc->lock);
22 for_each_possible_cpu(cpu) {
23 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
24 *pcount = 0;
25 }
26 fbc->count = amount;
27 spin_unlock(&fbc->lock);
28}
29EXPORT_SYMBOL(percpu_counter_set);
30
Peter Zijlstra20e89762007-10-16 23:25:43 -070031void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070032{
Peter Zijlstra20e89762007-10-16 23:25:43 -070033 s64 count;
Mingming Cao0216bfc2006-06-23 02:05:41 -070034 s32 *pcount;
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070035 int cpu = get_cpu();
36
37 pcount = per_cpu_ptr(fbc->counters, cpu);
38 count = *pcount + amount;
Peter Zijlstra252e0ba2007-10-16 23:25:43 -070039 if (count >= batch || count <= -batch) {
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070040 spin_lock(&fbc->lock);
41 fbc->count += count;
42 *pcount = 0;
43 spin_unlock(&fbc->lock);
44 } else {
45 *pcount = count;
46 }
47 put_cpu();
48}
Peter Zijlstra252e0ba2007-10-16 23:25:43 -070049EXPORT_SYMBOL(__percpu_counter_add);
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070050
51/*
52 * Add up all the per-cpu counts, return the result. This is a more accurate
53 * but much slower version of percpu_counter_read_positive()
54 */
Mingming Cao0216bfc2006-06-23 02:05:41 -070055s64 percpu_counter_sum(struct percpu_counter *fbc)
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070056{
Mingming Cao0216bfc2006-06-23 02:05:41 -070057 s64 ret;
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070058 int cpu;
59
60 spin_lock(&fbc->lock);
61 ret = fbc->count;
Andrew Mortonb4ef0292007-07-15 23:39:51 -070062 for_each_online_cpu(cpu) {
Mingming Cao0216bfc2006-06-23 02:05:41 -070063 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
Ravikiran G Thirumalai3cbc5642006-06-23 02:05:40 -070064 ret += *pcount;
65 }
66 spin_unlock(&fbc->lock);
67 return ret < 0 ? 0 : ret;
68}
69EXPORT_SYMBOL(percpu_counter_sum);
Andrew Mortonc67ad912007-07-15 23:39:51 -070070
71void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
72{
73 spin_lock_init(&fbc->lock);
74 fbc->count = amount;
75 fbc->counters = alloc_percpu(s32);
76#ifdef CONFIG_HOTPLUG_CPU
77 mutex_lock(&percpu_counters_lock);
78 list_add(&fbc->list, &percpu_counters);
79 mutex_unlock(&percpu_counters_lock);
80#endif
81}
82EXPORT_SYMBOL(percpu_counter_init);
83
84void percpu_counter_destroy(struct percpu_counter *fbc)
85{
86 free_percpu(fbc->counters);
87#ifdef CONFIG_HOTPLUG_CPU
88 mutex_lock(&percpu_counters_lock);
89 list_del(&fbc->list);
90 mutex_unlock(&percpu_counters_lock);
91#endif
92}
93EXPORT_SYMBOL(percpu_counter_destroy);
94
95#ifdef CONFIG_HOTPLUG_CPU
96static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
97 unsigned long action, void *hcpu)
98{
99 unsigned int cpu;
100 struct percpu_counter *fbc;
101
102 if (action != CPU_DEAD)
103 return NOTIFY_OK;
104
105 cpu = (unsigned long)hcpu;
106 mutex_lock(&percpu_counters_lock);
107 list_for_each_entry(fbc, &percpu_counters, list) {
108 s32 *pcount;
109
110 spin_lock(&fbc->lock);
111 pcount = per_cpu_ptr(fbc->counters, cpu);
112 fbc->count += *pcount;
113 *pcount = 0;
114 spin_unlock(&fbc->lock);
115 }
116 mutex_unlock(&percpu_counters_lock);
117 return NOTIFY_OK;
118}
119
120static int __init percpu_counter_startup(void)
121{
122 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
123 return 0;
124}
125module_init(percpu_counter_startup);
126#endif