2 * Fast batching percpu counters.
5 #include <linux/percpu_counter.h>
6 #include <linux/notifier.h>
7 #include <linux/mutex.h>
8 #include <linux/init.h>
10 #include <linux/module.h>
12 #ifdef CONFIG_HOTPLUG_CPU
13 static LIST_HEAD(percpu_counters);
14 static DEFINE_MUTEX(percpu_counters_lock);
17 void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
21 spin_lock(&fbc->lock);
22 for_each_possible_cpu(cpu) {
23 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
27 spin_unlock(&fbc->lock);
29 EXPORT_SYMBOL(percpu_counter_set);
31 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
37 pcount = per_cpu_ptr(fbc->counters, cpu);
38 count = *pcount + amount;
39 if (count >= batch || count <= -batch) {
40 spin_lock(&fbc->lock);
43 spin_unlock(&fbc->lock);
49 EXPORT_SYMBOL(__percpu_counter_add);
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()
55 s64 __percpu_counter_sum(struct percpu_counter *fbc)
60 spin_lock(&fbc->lock);
62 for_each_online_cpu(cpu) {
63 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
66 spin_unlock(&fbc->lock);
69 EXPORT_SYMBOL(__percpu_counter_sum);
71 int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
73 spin_lock_init(&fbc->lock);
75 fbc->counters = alloc_percpu(s32);
78 #ifdef CONFIG_HOTPLUG_CPU
79 mutex_lock(&percpu_counters_lock);
80 list_add(&fbc->list, &percpu_counters);
81 mutex_unlock(&percpu_counters_lock);
85 EXPORT_SYMBOL(percpu_counter_init);
87 void percpu_counter_destroy(struct percpu_counter *fbc)
92 free_percpu(fbc->counters);
93 #ifdef CONFIG_HOTPLUG_CPU
94 mutex_lock(&percpu_counters_lock);
96 mutex_unlock(&percpu_counters_lock);
99 EXPORT_SYMBOL(percpu_counter_destroy);
101 #ifdef CONFIG_HOTPLUG_CPU
102 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
103 unsigned long action, void *hcpu)
106 struct percpu_counter *fbc;
108 if (action != CPU_DEAD)
111 cpu = (unsigned long)hcpu;
112 mutex_lock(&percpu_counters_lock);
113 list_for_each_entry(fbc, &percpu_counters, list) {
116 spin_lock(&fbc->lock);
117 pcount = per_cpu_ptr(fbc->counters, cpu);
118 fbc->count += *pcount;
120 spin_unlock(&fbc->lock);
122 mutex_unlock(&percpu_counters_lock);
126 static int __init percpu_counter_startup(void)
128 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
131 module_init(percpu_counter_startup);