blob: bd6708e2c02703e70be886a4229eb4071be33137 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
|
#ifndef _LINUX_PERCPU_COUNTER_H
#define _LINUX_PERCPU_COUNTER_H
/*
* A simple "approximate counter" for use in ext2 and ext3 superblocks.
*
* WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
*/
#include <linux/config.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#ifdef CONFIG_SMP
struct percpu_counter {
spinlock_t lock;
long count;
long *counters;
};
#if NR_CPUS >= 16
#define FBC_BATCH (NR_CPUS*2)
#else
#define FBC_BATCH (NR_CPUS*4)
#endif
static inline void percpu_counter_init(struct percpu_counter *fbc)
{
spin_lock_init(&fbc->lock);
fbc->count = 0;
fbc->counters = alloc_percpu(long);
}
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
free_percpu(fbc->counters);
}
void percpu_counter_mod(struct percpu_counter *fbc, long amount);
static inline long percpu_counter_read(struct percpu_counter *fbc)
{
return fbc->count;
}
/*
* It is possible for the percpu_counter_read() to return a small negative
* number for some counter which should never be negative.
*/
static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
{
long ret = fbc->count;
barrier(); /* Prevent reloads of fbc->count */
if (ret > 0)
return ret;
return 1;
}
#else
struct percpu_counter {
long count;
};
static inline void percpu_counter_init(struct percpu_counter *fbc)
{
fbc->count = 0;
}
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}
static inline void
percpu_counter_mod(struct percpu_counter *fbc, long amount)
{
preempt_disable();
fbc->count += amount;
preempt_enable();
}
static inline long percpu_counter_read(struct percpu_counter *fbc)
{
return fbc->count;
}
static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
{
return fbc->count;
}
#endif /* CONFIG_SMP */
static inline void percpu_counter_inc(struct percpu_counter *fbc)
{
percpu_counter_mod(fbc, 1);
}
static inline void percpu_counter_dec(struct percpu_counter *fbc)
{
percpu_counter_mod(fbc, -1);
}
#endif /* _LINUX_PERCPU_COUNTER_H */
|
