[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>
This commit is contained in:
Arnaldo Carvalho de Melo 2007-11-21 22:02:58 +08:00 committed by David S. Miller
parent 0c884439db
commit de4d1db369
3 changed files with 129 additions and 0 deletions

102
include/linux/pcounter.h Normal file
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@ -0,0 +1,102 @@
#ifndef __LINUX_PCOUNTER_H
#define __LINUX_PCOUNTER_H
struct pcounter {
#ifdef CONFIG_SMP
void (*add)(struct pcounter *self, int inc);
int (*getval)(const struct pcounter *self);
int *per_cpu_values;
#else
int val;
#endif
};
/*
* Special macros to let pcounters use a fast version of {getvalue|add}
* using a static percpu variable per pcounter instead of an allocated one,
* saving one dereference.
* This might be changed if/when dynamic percpu vars become fast.
*/
#ifdef CONFIG_SMP
#include <linux/cpumask.h>
#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 inc) \
{ \
__get_cpu_var(NAME##_pcounter_values) += inc; \
} \
\
static int NAME##_pcounter_getval(const struct pcounter *self) \
{ \
int res = 0, cpu; \
\
for_each_possible_cpu(cpu) \
res += per_cpu(NAME##_pcounter_values, cpu); \
return res; \
}
#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
MEMBER = { \
.add = NAME##_pcounter_add, \
.getval = NAME##_pcounter_getval, \
}
extern void pcounter_def_add(struct pcounter *self, int inc);
extern int pcounter_def_getval(const struct pcounter *self);
static inline int pcounter_alloc(struct pcounter *self)
{
int rc = 0;
if (self->add == NULL) {
self->per_cpu_values = alloc_percpu(int);
if (self->per_cpu_values != NULL) {
self->add = pcounter_def_add;
self->getval = pcounter_def_getval;
} else
rc = 1;
}
return rc;
}
static inline void pcounter_free(struct pcounter *self)
{
if (self->per_cpu_values != NULL) {
free_percpu(self->per_cpu_values);
self->per_cpu_values = NULL;
self->getval = NULL;
self->add = NULL;
}
}
static inline void pcounter_add(struct pcounter *self, int inc)
{
self->add(self, inc);
}
static inline int pcounter_getval(const struct pcounter *self)
{
return self->getval(self);
}
#else /* CONFIG_SMP */
static inline void pcounter_add(struct pcounter *self, int inc)
{
self->value += 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 */

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@ -61,6 +61,7 @@ obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
obj-$(CONFIG_TEXTSEARCH_BM) += ts_bm.o
obj-$(CONFIG_TEXTSEARCH_FSM) += ts_fsm.o
obj-$(CONFIG_SMP) += percpu_counter.o
obj-$(CONFIG_SMP) += pcounter.o
obj-$(CONFIG_AUDIT_GENERIC) += audit.o
obj-$(CONFIG_SWIOTLB) += swiotlb.o

26
lib/pcounter.c Normal file
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@ -0,0 +1,26 @@
/*
* Define default pcounter functions
* Note that often used pcounters use dedicated functions to get a speed increase.
* (see DEFINE_PCOUNTER/REF_PCOUNTER_MEMBER)
*/
#include <linux/module.h>
#include <linux/pcounter.h>
#include <linux/smp.h>
void pcounter_def_add(struct pcounter *self, int inc)
{
per_cpu_ptr(self->per_cpu_values, smp_processor_id())[0] += inc;
}
EXPORT_SYMBOL_GPL(pcounter_def_add);
int pcounter_def_getval(const struct pcounter *self)
{
int res = 0, cpu;
for_each_possible_cpu(cpu)
res += per_cpu_ptr(self->per_cpu_values, cpu)[0];
return res;
}
EXPORT_SYMBOL_GPL(pcounter_def_getval);