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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 bool 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 true; | |
31 | default: | |
32 | return false; | |
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 | unsigned long flags; | |
64 | ||
65 | raw_spin_lock_irqsave(&fbc->lock, flags); | |
66 | for_each_possible_cpu(cpu) { | |
67 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); | |
68 | *pcount = 0; | |
69 | } | |
70 | fbc->count = amount; | |
71 | raw_spin_unlock_irqrestore(&fbc->lock, flags); | |
72 | } | |
73 | EXPORT_SYMBOL(percpu_counter_set); | |
74 | ||
75 | void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) | |
76 | { | |
77 | s64 count; | |
78 | ||
79 | preempt_disable(); | |
80 | count = __this_cpu_read(*fbc->counters) + amount; | |
81 | if (count >= batch || count <= -batch) { | |
82 | unsigned long flags; | |
83 | raw_spin_lock_irqsave(&fbc->lock, flags); | |
84 | fbc->count += count; | |
85 | __this_cpu_sub(*fbc->counters, count - amount); | |
86 | raw_spin_unlock_irqrestore(&fbc->lock, flags); | |
87 | } else { | |
88 | this_cpu_add(*fbc->counters, amount); | |
89 | } | |
90 | preempt_enable(); | |
91 | } | |
92 | EXPORT_SYMBOL(__percpu_counter_add); | |
93 | ||
94 | /* | |
95 | * Add up all the per-cpu counts, return the result. This is a more accurate | |
96 | * but much slower version of percpu_counter_read_positive() | |
97 | */ | |
98 | s64 __percpu_counter_sum(struct percpu_counter *fbc) | |
99 | { | |
100 | s64 ret; | |
101 | int cpu; | |
102 | unsigned long flags; | |
103 | ||
104 | raw_spin_lock_irqsave(&fbc->lock, flags); | |
105 | ret = fbc->count; | |
106 | for_each_online_cpu(cpu) { | |
107 | s32 *pcount = per_cpu_ptr(fbc->counters, cpu); | |
108 | ret += *pcount; | |
109 | } | |
110 | raw_spin_unlock_irqrestore(&fbc->lock, flags); | |
111 | return ret; | |
112 | } | |
113 | EXPORT_SYMBOL(__percpu_counter_sum); | |
114 | ||
115 | int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp, | |
116 | struct lock_class_key *key) | |
117 | { | |
118 | unsigned long flags __maybe_unused; | |
119 | ||
120 | raw_spin_lock_init(&fbc->lock); | |
121 | lockdep_set_class(&fbc->lock, key); | |
122 | fbc->count = amount; | |
123 | fbc->counters = alloc_percpu_gfp(s32, gfp); | |
124 | if (!fbc->counters) | |
125 | return -ENOMEM; | |
126 | ||
127 | debug_percpu_counter_activate(fbc); | |
128 | ||
129 | #ifdef CONFIG_HOTPLUG_CPU | |
130 | INIT_LIST_HEAD(&fbc->list); | |
131 | spin_lock_irqsave(&percpu_counters_lock, flags); | |
132 | list_add(&fbc->list, &percpu_counters); | |
133 | spin_unlock_irqrestore(&percpu_counters_lock, flags); | |
134 | #endif | |
135 | return 0; | |
136 | } | |
137 | EXPORT_SYMBOL(__percpu_counter_init); | |
138 | ||
139 | void percpu_counter_destroy(struct percpu_counter *fbc) | |
140 | { | |
141 | unsigned long flags __maybe_unused; | |
142 | ||
143 | if (!fbc->counters) | |
144 | return; | |
145 | ||
146 | debug_percpu_counter_deactivate(fbc); | |
147 | ||
148 | #ifdef CONFIG_HOTPLUG_CPU | |
149 | spin_lock_irqsave(&percpu_counters_lock, flags); | |
150 | list_del(&fbc->list); | |
151 | spin_unlock_irqrestore(&percpu_counters_lock, flags); | |
152 | #endif | |
153 | free_percpu(fbc->counters); | |
154 | fbc->counters = NULL; | |
155 | } | |
156 | EXPORT_SYMBOL(percpu_counter_destroy); | |
157 | ||
158 | int percpu_counter_batch __read_mostly = 32; | |
159 | EXPORT_SYMBOL(percpu_counter_batch); | |
160 | ||
161 | static int compute_batch_value(unsigned int cpu) | |
162 | { | |
163 | int nr = num_online_cpus(); | |
164 | ||
165 | percpu_counter_batch = max(32, nr*2); | |
166 | return 0; | |
167 | } | |
168 | ||
169 | static int percpu_counter_cpu_dead(unsigned int cpu) | |
170 | { | |
171 | #ifdef CONFIG_HOTPLUG_CPU | |
172 | struct percpu_counter *fbc; | |
173 | ||
174 | compute_batch_value(cpu); | |
175 | ||
176 | spin_lock_irq(&percpu_counters_lock); | |
177 | list_for_each_entry(fbc, &percpu_counters, list) { | |
178 | s32 *pcount; | |
179 | ||
180 | raw_spin_lock(&fbc->lock); | |
181 | pcount = per_cpu_ptr(fbc->counters, cpu); | |
182 | fbc->count += *pcount; | |
183 | *pcount = 0; | |
184 | raw_spin_unlock(&fbc->lock); | |
185 | } | |
186 | spin_unlock_irq(&percpu_counters_lock); | |
187 | #endif | |
188 | return 0; | |
189 | } | |
190 | ||
191 | /* | |
192 | * Compare counter against given value. | |
193 | * Return 1 if greater, 0 if equal and -1 if less | |
194 | */ | |
195 | int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch) | |
196 | { | |
197 | s64 count; | |
198 | ||
199 | count = percpu_counter_read(fbc); | |
200 | /* Check to see if rough count will be sufficient for comparison */ | |
201 | if (abs(count - rhs) > (batch * num_online_cpus())) { | |
202 | if (count > rhs) | |
203 | return 1; | |
204 | else | |
205 | return -1; | |
206 | } | |
207 | /* Need to use precise count */ | |
208 | count = percpu_counter_sum(fbc); | |
209 | if (count > rhs) | |
210 | return 1; | |
211 | else if (count < rhs) | |
212 | return -1; | |
213 | else | |
214 | return 0; | |
215 | } | |
216 | EXPORT_SYMBOL(__percpu_counter_compare); | |
217 | ||
218 | static int __init percpu_counter_startup(void) | |
219 | { | |
220 | int ret; | |
221 | ||
222 | ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "lib/percpu_cnt:online", | |
223 | compute_batch_value, NULL); | |
224 | WARN_ON(ret < 0); | |
225 | ret = cpuhp_setup_state_nocalls(CPUHP_PERCPU_CNT_DEAD, | |
226 | "lib/percpu_cnt:dead", NULL, | |
227 | percpu_counter_cpu_dead); | |
228 | WARN_ON(ret < 0); | |
229 | return 0; | |
230 | } | |
231 | module_init(percpu_counter_startup); |