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authorArnaldo Carvalho de Melo <acme@redhat.com>2007-11-21 09:02:58 -0500
committerDavid S. Miller <davem@davemloft.net>2008-01-28 17:54:39 -0500
commitde4d1db369785c29d68915edfee0cb70e8199f4c (patch)
tree78979fc131145d4b2df3cd4721a811784126f05c /include
parent0c884439dbd7c895cce61c4974c8868b0f6cd4a1 (diff)
[LIB]: Introduce struct pcounter
This just generalises what was introduced by Eric Dumazet for the struct proto inuse field in 286ab3d46058840d68e5d7d52e316c1f7e98c59f: [NET]: Define infrastructure to keep 'inuse' changes in an efficent SMP/NUMA way. Please look at the comment in there to see the rationale. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/pcounter.h102
1 files changed, 102 insertions, 0 deletions
diff --git a/include/linux/pcounter.h b/include/linux/pcounter.h
new file mode 100644
index 000000000000..620aaded4e94
--- /dev/null
+++ b/include/linux/pcounter.h
@@ -0,0 +1,102 @@
1#ifndef __LINUX_PCOUNTER_H
2#define __LINUX_PCOUNTER_H
3
4struct pcounter {
5#ifdef CONFIG_SMP
6 void (*add)(struct pcounter *self, int inc);
7 int (*getval)(const struct pcounter *self);
8 int *per_cpu_values;
9#else
10 int val;
11#endif
12};
13
14/*
15 * Special macros to let pcounters use a fast version of {getvalue|add}
16 * using a static percpu variable per pcounter instead of an allocated one,
17 * saving one dereference.
18 * This might be changed if/when dynamic percpu vars become fast.
19 */
20#ifdef CONFIG_SMP
21#include <linux/cpumask.h>
22#include <linux/percpu.h>
23
24#define DEFINE_PCOUNTER(NAME) \
25static DEFINE_PER_CPU(int, NAME##_pcounter_values); \
26static void NAME##_pcounter_add(struct pcounter *self, int inc) \
27{ \
28 __get_cpu_var(NAME##_pcounter_values) += inc; \
29} \
30 \
31static int NAME##_pcounter_getval(const struct pcounter *self) \
32{ \
33 int res = 0, cpu; \
34 \
35 for_each_possible_cpu(cpu) \
36 res += per_cpu(NAME##_pcounter_values, cpu); \
37 return res; \
38}
39
40#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
41 MEMBER = { \
42 .add = NAME##_pcounter_add, \
43 .getval = NAME##_pcounter_getval, \
44 }
45
46extern void pcounter_def_add(struct pcounter *self, int inc);
47extern int pcounter_def_getval(const struct pcounter *self);
48
49static inline int pcounter_alloc(struct pcounter *self)
50{
51 int rc = 0;
52 if (self->add == NULL) {
53 self->per_cpu_values = alloc_percpu(int);
54 if (self->per_cpu_values != NULL) {
55 self->add = pcounter_def_add;
56 self->getval = pcounter_def_getval;
57 } else
58 rc = 1;
59 }
60 return rc;
61}
62
63static inline void pcounter_free(struct pcounter *self)
64{
65 if (self->per_cpu_values != NULL) {
66 free_percpu(self->per_cpu_values);
67 self->per_cpu_values = NULL;
68 self->getval = NULL;
69 self->add = NULL;
70 }
71}
72
73static inline void pcounter_add(struct pcounter *self, int inc)
74{
75 self->add(self, inc);
76}
77
78static inline int pcounter_getval(const struct pcounter *self)
79{
80 return self->getval(self);
81}
82
83#else /* CONFIG_SMP */
84
85static inline void pcounter_add(struct pcounter *self, int inc)
86{
87 self->value += inc;
88}
89
90static inline int pcounter_getval(const struct pcounter *self)
91{
92 return self->val;
93}
94
95#define DEFINE_PCOUNTER(NAME)
96#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)
97#define pcounter_alloc(self) 0
98#define pcounter_free(self)
99
100#endif /* CONFIG_SMP */
101
102#endif /* __LINUX_PCOUNTER_H */