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1da177e4 LT |
1 | #ifndef _LINUX_PERCPU_COUNTER_H |
2 | #define _LINUX_PERCPU_COUNTER_H | |
3 | /* | |
4 | * A simple "approximate counter" for use in ext2 and ext3 superblocks. | |
5 | * | |
6 | * WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4. | |
7 | */ | |
8 | ||
9 | #include <linux/config.h> | |
10 | #include <linux/spinlock.h> | |
11 | #include <linux/smp.h> | |
12 | #include <linux/threads.h> | |
13 | #include <linux/percpu.h> | |
14 | ||
15 | #ifdef CONFIG_SMP | |
16 | ||
17 | struct percpu_counter { | |
18 | spinlock_t lock; | |
19 | long count; | |
20 | long *counters; | |
21 | }; | |
22 | ||
23 | #if NR_CPUS >= 16 | |
24 | #define FBC_BATCH (NR_CPUS*2) | |
25 | #else | |
26 | #define FBC_BATCH (NR_CPUS*4) | |
27 | #endif | |
28 | ||
29 | static inline void percpu_counter_init(struct percpu_counter *fbc) | |
30 | { | |
31 | spin_lock_init(&fbc->lock); | |
32 | fbc->count = 0; | |
33 | fbc->counters = alloc_percpu(long); | |
34 | } | |
35 | ||
36 | static inline void percpu_counter_destroy(struct percpu_counter *fbc) | |
37 | { | |
38 | free_percpu(fbc->counters); | |
39 | } | |
40 | ||
41 | void percpu_counter_mod(struct percpu_counter *fbc, long amount); | |
42 | ||
43 | static inline long percpu_counter_read(struct percpu_counter *fbc) | |
44 | { | |
45 | return fbc->count; | |
46 | } | |
47 | ||
48 | /* | |
49 | * It is possible for the percpu_counter_read() to return a small negative | |
50 | * number for some counter which should never be negative. | |
51 | */ | |
52 | static inline long percpu_counter_read_positive(struct percpu_counter *fbc) | |
53 | { | |
54 | long ret = fbc->count; | |
55 | ||
56 | barrier(); /* Prevent reloads of fbc->count */ | |
57 | if (ret > 0) | |
58 | return ret; | |
59 | return 1; | |
60 | } | |
61 | ||
62 | #else | |
63 | ||
64 | struct percpu_counter { | |
65 | long count; | |
66 | }; | |
67 | ||
68 | static inline void percpu_counter_init(struct percpu_counter *fbc) | |
69 | { | |
70 | fbc->count = 0; | |
71 | } | |
72 | ||
73 | static inline void percpu_counter_destroy(struct percpu_counter *fbc) | |
74 | { | |
75 | } | |
76 | ||
77 | static inline void | |
78 | percpu_counter_mod(struct percpu_counter *fbc, long amount) | |
79 | { | |
80 | preempt_disable(); | |
81 | fbc->count += amount; | |
82 | preempt_enable(); | |
83 | } | |
84 | ||
85 | static inline long percpu_counter_read(struct percpu_counter *fbc) | |
86 | { | |
87 | return fbc->count; | |
88 | } | |
89 | ||
90 | static inline long percpu_counter_read_positive(struct percpu_counter *fbc) | |
91 | { | |
92 | return fbc->count; | |
93 | } | |
94 | ||
95 | #endif /* CONFIG_SMP */ | |
96 | ||
97 | static inline void percpu_counter_inc(struct percpu_counter *fbc) | |
98 | { | |
99 | percpu_counter_mod(fbc, 1); | |
100 | } | |
101 | ||
102 | static inline void percpu_counter_dec(struct percpu_counter *fbc) | |
103 | { | |
104 | percpu_counter_mod(fbc, -1); | |
105 | } | |
106 | ||
107 | #endif /* _LINUX_PERCPU_COUNTER_H */ |