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Commit de4d1db3 authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo Committed by David S. Miller
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[LIB]: Introduce struct pcounter 



This just generalises what was introduced by Eric Dumazet for the struct proto
inuse field in 286ab3d4:

    [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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0c884439

include/linux/pcounter.h

0 → 100644
+102 −0
Original line number Diff line number Diff line 
#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 */

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

lib/pcounter.c

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/*

 * 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);