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
|
#ifndef __LINUX_PCOUNTER_H
#define __LINUX_PCOUNTER_H
/*
* Using a dynamic percpu 'int' variable has a cost :
* 1) Extra dereference
* Current per_cpu_ptr() implementation uses an array per 'percpu variable'.
* 2) memory cost of NR_CPUS*(32+sizeof(void *)) instead of num_possible_cpus()*4
*
* This pcounter implementation is an abstraction to be able to use
* either a static or a dynamic per cpu variable.
* One dynamic per cpu variable gets a fast & cheap implementation, we can
* change pcounter implementation too.
*/
struct pcounter {
#ifdef CONFIG_SMP
void (*add)(struct pcounter *self, int inc);
int (*getval)(const struct pcounter *self, int cpu);
int *per_cpu_values;
#else
int val;
#endif
};
#ifdef CONFIG_SMP
#include <linux/percpu.h>
#define DEFINE_PCOUNTER(NAME) \
static DEFINE_PER_CPU(int, NAME##_pcounter_values); \
static void NAME##_pcounter_add(struct pcounter *self, int val) \
{ \
__get_cpu_var(NAME##_pcounter_values) += val; \
} \
static int NAME##_pcounter_getval(const struct pcounter *self, int cpu) \
{ \
return per_cpu(NAME##_pcounter_values, cpu); \
} \
#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
MEMBER = { \
.add = NAME##_pcounter_add, \
.getval = NAME##_pcounter_getval, \
}
static inline void pcounter_add(struct pcounter *self, int inc)
{
self->add(self, inc);
}
extern int pcounter_getval(const struct pcounter *self);
extern int pcounter_alloc(struct pcounter *self);
extern void pcounter_free(struct pcounter *self);
#else /* CONFIG_SMP */
static inline void pcounter_add(struct pcounter *self, int inc)
{
self->val += inc;
}
static inline int pcounter_getval(const struct pcounter *self)
{
return self->val;
}
#define DEFINE_PCOUNTER(NAME)
#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)
#define pcounter_alloc(self) 0
#define pcounter_free(self)
#endif /* CONFIG_SMP */
#endif /* __LINUX_PCOUNTER_H */
|
