Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#ifndef __LINUX_PCOUNTER_H
2#define __LINUX_PCOUNTER_H
3/*
4 * Using a dynamic percpu 'int' variable has a cost :
5 * 1) Extra dereference
6 * Current per_cpu_ptr() implementation uses an array per 'percpu variable'.
7 * 2) memory cost of NR_CPUS*(32+sizeof(void *)) instead of num_possible_cpus()*4
8 *
9 * This pcounter implementation is an abstraction to be able to use
10 * either a static or a dynamic per cpu variable.
11 * One dynamic per cpu variable gets a fast & cheap implementation, we can
12 * change pcounter implementation too.
13 */
14struct pcounter {
15#ifdef CONFIG_SMP
16 void (*add)(struct pcounter *self, int inc);
17 int (*getval)(const struct pcounter *self, int cpu);
18 int *per_cpu_values;
19#else
20 int val;
21#endif
22};
23
24#ifdef CONFIG_SMP
25#include <linux/percpu.h>
26
27#define DEFINE_PCOUNTER(NAME) \
28static DEFINE_PER_CPU(int, NAME##_pcounter_values); \
29static void NAME##_pcounter_add(struct pcounter *self, int val) \
30{ \
31 __get_cpu_var(NAME##_pcounter_values) += val; \
32} \
33static int NAME##_pcounter_getval(const struct pcounter *self, int cpu) \
34{ \
35 return per_cpu(NAME##_pcounter_values, cpu); \
36} \
37
38#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
39 MEMBER = { \
40 .add = NAME##_pcounter_add, \
41 .getval = NAME##_pcounter_getval, \
42 }
43
44
45static inline void pcounter_add(struct pcounter *self, int inc)
46{
47 self->add(self, inc);
48}
49
50extern int pcounter_getval(const struct pcounter *self);
51extern int pcounter_alloc(struct pcounter *self);
52extern void pcounter_free(struct pcounter *self);
53
54
55#else /* CONFIG_SMP */
56
57static inline void pcounter_add(struct pcounter *self, int inc)
58{
59 self->val += inc;
60}
61
62static inline int pcounter_getval(const struct pcounter *self)
63{
64 return self->val;
65}
66
67#define DEFINE_PCOUNTER(NAME)
68#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)
69#define pcounter_alloc(self) 0
70#define pcounter_free(self)
71
72#endif /* CONFIG_SMP */
73
74#endif /* __LINUX_PCOUNTER_H */