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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 | ||
12 | static LIST_HEAD(percpu_counters); | |
13 | static DEFINE_MUTEX(percpu_counters_lock); | |
14 | ||
15 | void percpu_counter_set(struct percpu_counter *fbc, s64 amount) | |
16 | { | |
17 | int cpu; | |
18 | ||
19 | spin_lock(&fbc->lock); | |
20 | for_each_possible_cpu(cpu) { | |
21 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); | |
22 | *pcount = 0; | |
23 | } | |
24 | fbc->count = amount; | |
25 | spin_unlock(&fbc->lock); | |
26 | } | |
27 | EXPORT_SYMBOL(percpu_counter_set); | |
28 | ||
29 | void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) | |
30 | { | |
31 | s64 count; | |
32 | s32 *pcount; | |
33 | int cpu = get_cpu(); | |
34 | ||
35 | pcount = per_cpu_ptr(fbc->counters, cpu); | |
36 | count = *pcount + amount; | |
37 | if (count >= batch || count <= -batch) { | |
38 | spin_lock(&fbc->lock); | |
39 | fbc->count += count; | |
40 | *pcount = 0; | |
41 | spin_unlock(&fbc->lock); | |
42 | } else { | |
43 | *pcount = count; | |
44 | } | |
45 | put_cpu(); | |
46 | } | |
47 | EXPORT_SYMBOL(__percpu_counter_add); | |
48 | ||
49 | /* | |
50 | * Add up all the per-cpu counts, return the result. This is a more accurate | |
51 | * but much slower version of percpu_counter_read_positive() | |
52 | */ | |
53 | s64 __percpu_counter_sum(struct percpu_counter *fbc) | |
54 | { | |
55 | s64 ret; | |
56 | int cpu; | |
57 | ||
58 | spin_lock(&fbc->lock); | |
59 | ret = fbc->count; | |
60 | for_each_online_cpu(cpu) { | |
61 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); | |
62 | ret += *pcount; | |
63 | } | |
64 | spin_unlock(&fbc->lock); | |
65 | return ret; | |
66 | } | |
67 | EXPORT_SYMBOL(__percpu_counter_sum); | |
68 | ||
69 | int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, | |
70 | struct lock_class_key *key) | |
71 | { | |
72 | spin_lock_init(&fbc->lock); | |
73 | lockdep_set_class(&fbc->lock, key); | |
74 | fbc->count = amount; | |
75 | fbc->counters = alloc_percpu(s32); | |
76 | if (!fbc->counters) | |
77 | return -ENOMEM; | |
78 | #ifdef CONFIG_HOTPLUG_CPU | |
79 | mutex_lock(&percpu_counters_lock); | |
80 | list_add(&fbc->list, &percpu_counters); | |
81 | mutex_unlock(&percpu_counters_lock); | |
82 | #endif | |
83 | return 0; | |
84 | } | |
85 | EXPORT_SYMBOL(__percpu_counter_init); | |
86 | ||
87 | void percpu_counter_destroy(struct percpu_counter *fbc) | |
88 | { | |
89 | if (!fbc->counters) | |
90 | return; | |
91 | ||
92 | #ifdef CONFIG_HOTPLUG_CPU | |
93 | mutex_lock(&percpu_counters_lock); | |
94 | list_del(&fbc->list); | |
95 | mutex_unlock(&percpu_counters_lock); | |
96 | #endif | |
97 | free_percpu(fbc->counters); | |
98 | fbc->counters = NULL; | |
99 | } | |
100 | EXPORT_SYMBOL(percpu_counter_destroy); | |
101 | ||
102 | int percpu_counter_batch __read_mostly = 32; | |
103 | EXPORT_SYMBOL(percpu_counter_batch); | |
104 | ||
105 | static void compute_batch_value(void) | |
106 | { | |
107 | int nr = num_online_cpus(); | |
108 | ||
109 | percpu_counter_batch = max(32, nr*2); | |
110 | } | |
111 | ||
112 | static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, | |
113 | unsigned long action, void *hcpu) | |
114 | { | |
115 | #ifdef CONFIG_HOTPLUG_CPU | |
116 | unsigned int cpu; | |
117 | struct percpu_counter *fbc; | |
118 | ||
119 | compute_batch_value(); | |
120 | if (action != CPU_DEAD) | |
121 | return NOTIFY_OK; | |
122 | ||
123 | cpu = (unsigned long)hcpu; | |
124 | mutex_lock(&percpu_counters_lock); | |
125 | list_for_each_entry(fbc, &percpu_counters, list) { | |
126 | s32 *pcount; | |
127 | unsigned long flags; | |
128 | ||
129 | spin_lock_irqsave(&fbc->lock, flags); | |
130 | pcount = per_cpu_ptr(fbc->counters, cpu); | |
131 | fbc->count += *pcount; | |
132 | *pcount = 0; | |
133 | spin_unlock_irqrestore(&fbc->lock, flags); | |
134 | } | |
135 | mutex_unlock(&percpu_counters_lock); | |
136 | #endif | |
137 | return NOTIFY_OK; | |
138 | } | |
139 | ||
140 | static int __init percpu_counter_startup(void) | |
141 | { | |
142 | compute_batch_value(); | |
143 | hotcpu_notifier(percpu_counter_hotcpu_callback, 0); | |
144 | return 0; | |
145 | } | |
146 | module_init(percpu_counter_startup); |