Commit 571e7682 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 789675e2

include/linux/pcounter.h

+26 −54
Original line number Diff line number Diff line 
#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)	\

static void NAME##_pcounter_add(struct pcounter *self, int val)		\

{									\

       __get_cpu_var(NAME##_pcounter_values) += inc;		\

       __get_cpu_var(NAME##_pcounter_values) += val;			\

}									\

								\

static int NAME##_pcounter_getval(const struct pcounter *self)	\

static int NAME##_pcounter_getval(const struct pcounter *self, int cpu)	\

{									\

       int res = 0, cpu;					\

								\

       for_each_possible_cpu(cpu)				\

               res += per_cpu(NAME##_pcounter_values, cpu);	\

       return res;						\

}

	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 */

lib/pcounter.c

+37 −5
Original line number Diff line number Diff line
@@ -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);

static int pcounter_dyn_getval(const struct pcounter *self, int cpu)

{

	return per_cpu_ptr(self->per_cpu_values, cpu)[0];

}



int pcounter_def_getval(const struct pcounter *self)

int pcounter_getval(const struct pcounter *self)

{

	int res = 0, cpu;



	for_each_possible_cpu(cpu)

		res += per_cpu_ptr(self->per_cpu_values, cpu)[0];

		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);

EXPORT_SYMBOL_GPL(pcounter_def_getval);

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