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Commit b2e8fb6e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

mm: scalable bdi statistics counters 



Provide scalable per backing_dev_info statistics counters.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e0bf68dd

include/linux/backing-dev.h

+82 −3
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#ifndef _LINUX_BACKING_DEV_H

#define _LINUX_BACKING_DEV_H



#include <linux/percpu_counter.h>

#include <linux/log2.h>

#include <asm/atomic.h>



struct page;
@@ -24,6 +26,12 @@ enum bdi_state { 


typedef int (congested_fn)(void *, int);



enum bdi_stat_item {

	NR_BDI_STAT_ITEMS

};



#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))



struct backing_dev_info {

	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */

	unsigned long state;	/* Always use atomic bitops on this */
@@ -32,15 +40,86 @@ struct backing_dev_info { 
	void *congested_data;	/* Pointer to aux data for congested func */

	void (*unplug_io_fn)(struct backing_dev_info *, struct page *);

	void *unplug_io_data;



	struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];

};



static inline int bdi_init(struct backing_dev_info *bdi)

int bdi_init(struct backing_dev_info *bdi);

void bdi_destroy(struct backing_dev_info *bdi);



static inline void __add_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item, s64 amount)

{

	return 0;

	__percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);

}



static inline void bdi_destroy(struct backing_dev_info *bdi)

static inline void __inc_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	__add_bdi_stat(bdi, item, 1);

}



static inline void inc_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	unsigned long flags;



	local_irq_save(flags);

	__inc_bdi_stat(bdi, item);

	local_irq_restore(flags);

}



static inline void __dec_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	__add_bdi_stat(bdi, item, -1);

}



static inline void dec_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	unsigned long flags;



	local_irq_save(flags);

	__dec_bdi_stat(bdi, item);

	local_irq_restore(flags);

}



static inline s64 bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	return percpu_counter_read_positive(&bdi->bdi_stat[item]);

}



static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	return percpu_counter_sum_positive(&bdi->bdi_stat[item]);

}



static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

{

	s64 sum;

	unsigned long flags;



	local_irq_save(flags);

	sum = __bdi_stat_sum(bdi, item);

	local_irq_restore(flags);



	return sum;

}



/*

 * maximal error of a stat counter.

 */

static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)

{

#ifdef CONFIG_SMP

	return nr_cpu_ids * BDI_STAT_BATCH;

#else

	return 1;

#endif

}



/*

mm/backing-dev.c

+27 −0
Original line number Diff line number Diff line
@@ -5,6 +5,33 @@ 
#include <linux/sched.h>

#include <linux/module.h>



int bdi_init(struct backing_dev_info *bdi)

{

	int i, j;

	int err;



	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {

		err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);

		if (err) {

			for (j = 0; j < i; j++)

				percpu_counter_destroy(&bdi->bdi_stat[i]);

			break;

		}

	}



	return err;

}

EXPORT_SYMBOL(bdi_init);



void bdi_destroy(struct backing_dev_info *bdi)

{

	int i;



	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)

		percpu_counter_destroy(&bdi->bdi_stat[i]);

}

EXPORT_SYMBOL(bdi_destroy);



static wait_queue_head_t congestion_wqh[2] = {

		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),

		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])