linux-stable/include/linux/pcounter.h
Eric Dumazet 571e768202 [LIB] pcounter : unline too big functions
Before pushing pcounter to Linus tree, I would like to make some adjustments.

Goal is to reduce kernel text size, by unlining too big functions.

When a pcounter is bound to a statically defined per_cpu variable,
we define two small helpers functions. (No more folding function
using the fat for_each_possible_cpu(cpu) ... )

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);
}

Fast path is therefore unchanged, while folding/alloc/free is now unlined.

This saves 228 bytes on i386

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 15:00:35 -08:00

74 lines
1.9 KiB
C

#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 */