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Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago. By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing | |
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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 | #include <linux/debugobjects.h> |
12 | |
13 | #ifdef CONFIG_HOTPLUG_CPU |
14 | static LIST_HEAD(percpu_counters); |
15 | static DEFINE_SPINLOCK(percpu_counters_lock); |
16 | #endif |
17 | |
18 | #ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER |
19 | |
20 | static struct debug_obj_descr percpu_counter_debug_descr; |
21 | |
22 | static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state) |
23 | { |
24 | struct percpu_counter *fbc = addr; |
25 | |
26 | switch (state) { |
27 | case ODEBUG_STATE_ACTIVE: |
28 | percpu_counter_destroy(fbc); |
29 | debug_object_free(fbc, &percpu_counter_debug_descr); |
30 | return 1; |
31 | default: |
32 | return 0; |
33 | } |
34 | } |
35 | |
36 | static struct debug_obj_descr percpu_counter_debug_descr = { |
37 | .name = "percpu_counter", |
38 | .fixup_free = percpu_counter_fixup_free, |
39 | }; |
40 | |
41 | static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) |
42 | { |
43 | debug_object_init(fbc, &percpu_counter_debug_descr); |
44 | debug_object_activate(fbc, &percpu_counter_debug_descr); |
45 | } |
46 | |
47 | static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) |
48 | { |
49 | debug_object_deactivate(fbc, &percpu_counter_debug_descr); |
50 | debug_object_free(fbc, &percpu_counter_debug_descr); |
51 | } |
52 | |
53 | #else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ |
54 | static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) |
55 | { } |
56 | static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) |
57 | { } |
58 | #endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ |
59 | |
60 | void percpu_counter_set(struct percpu_counter *fbc, s64 amount) |
61 | { |
62 | int cpu; |
63 | |
64 | raw_spin_lock(&fbc->lock); |
65 | for_each_possible_cpu(cpu) { |
66 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); |
67 | *pcount = 0; |
68 | } |
69 | fbc->count = amount; |
70 | raw_spin_unlock(&fbc->lock); |
71 | } |
72 | EXPORT_SYMBOL(percpu_counter_set); |
73 | |
74 | void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) |
75 | { |
76 | s64 count; |
77 | |
78 | preempt_disable(); |
79 | count = __this_cpu_read(*fbc->counters) + amount; |
80 | if (count >= batch || count <= -batch) { |
81 | raw_spin_lock(&fbc->lock); |
82 | fbc->count += count; |
83 | __this_cpu_write(*fbc->counters, 0); |
84 | raw_spin_unlock(&fbc->lock); |
85 | } else { |
86 | __this_cpu_write(*fbc->counters, count); |
87 | } |
88 | preempt_enable(); |
89 | } |
90 | EXPORT_SYMBOL(__percpu_counter_add); |
91 | |
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 | */ |
96 | s64 __percpu_counter_sum(struct percpu_counter *fbc) |
97 | { |
98 | s64 ret; |
99 | int cpu; |
100 | |
101 | raw_spin_lock(&fbc->lock); |
102 | ret = fbc->count; |
103 | for_each_online_cpu(cpu) { |
104 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); |
105 | ret += *pcount; |
106 | } |
107 | raw_spin_unlock(&fbc->lock); |
108 | return ret; |
109 | } |
110 | EXPORT_SYMBOL(__percpu_counter_sum); |
111 | |
112 | int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, |
113 | struct lock_class_key *key) |
114 | { |
115 | raw_spin_lock_init(&fbc->lock); |
116 | lockdep_set_class(&fbc->lock, key); |
117 | fbc->count = amount; |
118 | fbc->counters = alloc_percpu(s32); |
119 | if (!fbc->counters) |
120 | return -ENOMEM; |
121 | |
122 | debug_percpu_counter_activate(fbc); |
123 | |
124 | #ifdef CONFIG_HOTPLUG_CPU |
125 | INIT_LIST_HEAD(&fbc->list); |
126 | spin_lock(&percpu_counters_lock); |
127 | list_add(&fbc->list, &percpu_counters); |
128 | spin_unlock(&percpu_counters_lock); |
129 | #endif |
130 | return 0; |
131 | } |
132 | EXPORT_SYMBOL(__percpu_counter_init); |
133 | |
134 | void percpu_counter_destroy(struct percpu_counter *fbc) |
135 | { |
136 | if (!fbc->counters) |
137 | return; |
138 | |
139 | debug_percpu_counter_deactivate(fbc); |
140 | |
141 | #ifdef CONFIG_HOTPLUG_CPU |
142 | spin_lock(&percpu_counters_lock); |
143 | list_del(&fbc->list); |
144 | spin_unlock(&percpu_counters_lock); |
145 | #endif |
146 | free_percpu(fbc->counters); |
147 | fbc->counters = NULL; |
148 | } |
149 | EXPORT_SYMBOL(percpu_counter_destroy); |
150 | |
151 | int percpu_counter_batch __read_mostly = 32; |
152 | EXPORT_SYMBOL(percpu_counter_batch); |
153 | |
154 | static void compute_batch_value(void) |
155 | { |
156 | int nr = num_online_cpus(); |
157 | |
158 | percpu_counter_batch = max(32, nr*2); |
159 | } |
160 | |
161 | static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, |
162 | unsigned long action, void *hcpu) |
163 | { |
164 | #ifdef CONFIG_HOTPLUG_CPU |
165 | unsigned int cpu; |
166 | struct percpu_counter *fbc; |
167 | |
168 | compute_batch_value(); |
169 | if (action != CPU_DEAD) |
170 | return NOTIFY_OK; |
171 | |
172 | cpu = (unsigned long)hcpu; |
173 | spin_lock(&percpu_counters_lock); |
174 | list_for_each_entry(fbc, &percpu_counters, list) { |
175 | s32 *pcount; |
176 | unsigned long flags; |
177 | |
178 | raw_spin_lock_irqsave(&fbc->lock, flags); |
179 | pcount = per_cpu_ptr(fbc->counters, cpu); |
180 | fbc->count += *pcount; |
181 | *pcount = 0; |
182 | raw_spin_unlock_irqrestore(&fbc->lock, flags); |
183 | } |
184 | spin_unlock(&percpu_counters_lock); |
185 | #endif |
186 | return NOTIFY_OK; |
187 | } |
188 | |
189 | /* |
190 | * Compare counter against given value. |
191 | * Return 1 if greater, 0 if equal and -1 if less |
192 | */ |
193 | int 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 | } |
214 | EXPORT_SYMBOL(percpu_counter_compare); |
215 | |
216 | static int __init percpu_counter_startup(void) |
217 | { |
218 | compute_batch_value(); |
219 | hotcpu_notifier(percpu_counter_hotcpu_callback, 0); |
220 | return 0; |
221 | } |
222 | module_init(percpu_counter_startup); |
223 |
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Tags:
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od-2011-09-18
v2.6.34-rc5
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