Commit | Line | Data |
---|---|---|
3cbc5640 RT |
1 | /* |
2 | * Fast batching percpu counters. | |
3 | */ | |
4 | ||
5 | #include <linux/percpu_counter.h> | |
c67ad917 AM |
6 | #include <linux/notifier.h> |
7 | #include <linux/mutex.h> | |
8 | #include <linux/init.h> | |
9 | #include <linux/cpu.h> | |
3cbc5640 | 10 | #include <linux/module.h> |
e2852ae8 | 11 | #include <linux/debugobjects.h> |
3cbc5640 | 12 | |
c67ad917 AM |
13 | static LIST_HEAD(percpu_counters); |
14 | static DEFINE_MUTEX(percpu_counters_lock); | |
c67ad917 | 15 | |
e2852ae8 TH |
16 | #ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER |
17 | ||
18 | static struct debug_obj_descr percpu_counter_debug_descr; | |
19 | ||
20 | static 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 | ||
34 | static struct debug_obj_descr percpu_counter_debug_descr = { | |
35 | .name = "percpu_counter", | |
36 | .fixup_free = percpu_counter_fixup_free, | |
37 | }; | |
38 | ||
39 | static 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 | ||
45 | static 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 */ | |
52 | static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) | |
53 | { } | |
54 | static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) | |
55 | { } | |
56 | #endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ | |
57 | ||
3a587f47 PZ |
58 | void 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 | } | |
70 | EXPORT_SYMBOL(percpu_counter_set); | |
71 | ||
20e89767 | 72 | void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) |
3cbc5640 | 73 | { |
20e89767 | 74 | s64 count; |
3cbc5640 | 75 | |
ea00c30b | 76 | preempt_disable(); |
819a72af | 77 | count = __this_cpu_read(*fbc->counters) + amount; |
252e0ba6 | 78 | if (count >= batch || count <= -batch) { |
3cbc5640 RT |
79 | spin_lock(&fbc->lock); |
80 | fbc->count += count; | |
819a72af | 81 | __this_cpu_write(*fbc->counters, 0); |
3cbc5640 RT |
82 | spin_unlock(&fbc->lock); |
83 | } else { | |
819a72af | 84 | __this_cpu_write(*fbc->counters, count); |
3cbc5640 | 85 | } |
ea00c30b | 86 | preempt_enable(); |
3cbc5640 | 87 | } |
252e0ba6 | 88 | EXPORT_SYMBOL(__percpu_counter_add); |
3cbc5640 RT |
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 | */ | |
02d21168 | 94 | s64 __percpu_counter_sum(struct percpu_counter *fbc) |
3cbc5640 | 95 | { |
0216bfcf | 96 | s64 ret; |
3cbc5640 RT |
97 | int cpu; |
98 | ||
99 | spin_lock(&fbc->lock); | |
100 | ret = fbc->count; | |
b4ef0296 | 101 | for_each_online_cpu(cpu) { |
0216bfcf | 102 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); |
3cbc5640 RT |
103 | ret += *pcount; |
104 | } | |
105 | spin_unlock(&fbc->lock); | |
bf1d89c8 | 106 | return ret; |
3cbc5640 | 107 | } |
bf1d89c8 | 108 | EXPORT_SYMBOL(__percpu_counter_sum); |
c67ad917 | 109 | |
ea319518 PZ |
110 | int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, |
111 | struct lock_class_key *key) | |
c67ad917 AM |
112 | { |
113 | spin_lock_init(&fbc->lock); | |
ea319518 | 114 | lockdep_set_class(&fbc->lock, key); |
c67ad917 AM |
115 | fbc->count = amount; |
116 | fbc->counters = alloc_percpu(s32); | |
833f4077 PZ |
117 | if (!fbc->counters) |
118 | return -ENOMEM; | |
e2852ae8 TH |
119 | |
120 | debug_percpu_counter_activate(fbc); | |
121 | ||
c67ad917 | 122 | #ifdef CONFIG_HOTPLUG_CPU |
8474b591 | 123 | INIT_LIST_HEAD(&fbc->list); |
c67ad917 AM |
124 | mutex_lock(&percpu_counters_lock); |
125 | list_add(&fbc->list, &percpu_counters); | |
126 | mutex_unlock(&percpu_counters_lock); | |
127 | #endif | |
833f4077 | 128 | return 0; |
c67ad917 | 129 | } |
ea319518 | 130 | EXPORT_SYMBOL(__percpu_counter_init); |
c67ad917 AM |
131 | |
132 | void percpu_counter_destroy(struct percpu_counter *fbc) | |
133 | { | |
833f4077 PZ |
134 | if (!fbc->counters) |
135 | return; | |
136 | ||
e2852ae8 TH |
137 | debug_percpu_counter_deactivate(fbc); |
138 | ||
c67ad917 AM |
139 | #ifdef CONFIG_HOTPLUG_CPU |
140 | mutex_lock(&percpu_counters_lock); | |
141 | list_del(&fbc->list); | |
142 | mutex_unlock(&percpu_counters_lock); | |
143 | #endif | |
fd3d664f ED |
144 | free_percpu(fbc->counters); |
145 | fbc->counters = NULL; | |
c67ad917 AM |
146 | } |
147 | EXPORT_SYMBOL(percpu_counter_destroy); | |
148 | ||
179f7ebf ED |
149 | int percpu_counter_batch __read_mostly = 32; |
150 | EXPORT_SYMBOL(percpu_counter_batch); | |
151 | ||
152 | static void compute_batch_value(void) | |
153 | { | |
154 | int nr = num_online_cpus(); | |
155 | ||
156 | percpu_counter_batch = max(32, nr*2); | |
157 | } | |
158 | ||
c67ad917 AM |
159 | static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, |
160 | unsigned long action, void *hcpu) | |
161 | { | |
179f7ebf | 162 | #ifdef CONFIG_HOTPLUG_CPU |
c67ad917 AM |
163 | unsigned int cpu; |
164 | struct percpu_counter *fbc; | |
165 | ||
179f7ebf | 166 | compute_batch_value(); |
c67ad917 AM |
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; | |
d2b20b11 | 174 | unsigned long flags; |
c67ad917 | 175 | |
d2b20b11 | 176 | spin_lock_irqsave(&fbc->lock, flags); |
c67ad917 AM |
177 | pcount = per_cpu_ptr(fbc->counters, cpu); |
178 | fbc->count += *pcount; | |
179 | *pcount = 0; | |
d2b20b11 | 180 | spin_unlock_irqrestore(&fbc->lock, flags); |
c67ad917 AM |
181 | } |
182 | mutex_unlock(&percpu_counters_lock); | |
179f7ebf | 183 | #endif |
c67ad917 AM |
184 | return NOTIFY_OK; |
185 | } | |
186 | ||
27f5e0f6 TC |
187 | /* |
188 | * Compare counter against given value. | |
189 | * Return 1 if greater, 0 if equal and -1 if less | |
190 | */ | |
191 | int 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 | } | |
212 | EXPORT_SYMBOL(percpu_counter_compare); | |
213 | ||
c67ad917 AM |
214 | static int __init percpu_counter_startup(void) |
215 | { | |
179f7ebf | 216 | compute_batch_value(); |
c67ad917 AM |
217 | hotcpu_notifier(percpu_counter_hotcpu_callback, 0); |
218 | return 0; | |
219 | } | |
220 | module_init(percpu_counter_startup); |