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[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>
This commit is contained in:
Eric Dumazet 2008-01-03 20:41:28 -08:00 committed by David S. Miller
parent 789675e216
commit 571e768202
2 changed files with 67 additions and 63 deletions
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80
include/linux/pcounter.h
View File

@ -1,41 +1,39 @@
#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 (*getval)(const struct pcounter *self, int cpu);
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 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 = { \
@ -43,42 +41,16 @@ static int NAME##_pcounter_getval(const struct pcounter *self) \
.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);
}
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 */

50
lib/pcounter.c
View File

@ -7,20 +7,52 @@
#include <linux/module.h>
#include <linux/pcounter.h>
#include <linux/smp.h>
#include <linux/cpumask.h>
void pcounter_def_add(struct pcounter *self, int inc)
static void pcounter_dyn_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)
static int pcounter_dyn_getval(const struct pcounter *self, int cpu)
{
int res = 0, cpu;
for_each_possible_cpu(cpu)
res += per_cpu_ptr(self->per_cpu_values, cpu)[0];
return res;
return per_cpu_ptr(self->per_cpu_values, cpu)[0];
}
EXPORT_SYMBOL_GPL(pcounter_def_getval);
int pcounter_getval(const struct pcounter *self)
{
int res = 0, cpu;
for_each_possible_cpu(cpu)
res += self->getval(self, cpu);
return res;
}
EXPORT_SYMBOL_GPL(pcounter_getval);
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_dyn_add;
self->getval = pcounter_dyn_getval;
} else
rc = 1;
}
return rc;
}
EXPORT_SYMBOL_GPL(pcounter_alloc);
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;
}
}
EXPORT_SYMBOL_GPL(pcounter_free);