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Commit 275f495d authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Linus Torvalds
Browse files

hpfs: implement prefetch to improve performance 



This patch implements prefetch to improve performance.  It helps mostly
when scanning the bitmaps to calculate free space.

Signed-off-by: default avatarMikulas Patocka <mpatocka@artax.karlin.mff.cuni.cz>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a0c1b759

fs/hpfs/buffer.c

+33 −0
Original line number Diff line number Diff line
@@ -7,8 +7,37 @@ 
 */

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/blkdev.h>

#include "hpfs_fn.h"



void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)

{

	struct buffer_head *bh;

	struct blk_plug plug;



	if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))

		return;



	bh = sb_find_get_block(s, secno);

	if (bh) {

		if (buffer_uptodate(bh)) {

			brelse(bh);

			return;

		}

		brelse(bh);

	};



	blk_start_plug(&plug);

	while (n > 0) {

		if (unlikely(secno >= hpfs_sb(s)->sb_fs_size))

			break;

		sb_breadahead(s, secno);

		secno++;

		n--;

	}

	blk_finish_plug(&plug);

}



/* Map a sector into a buffer and return pointers to it and to the buffer. */



void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp,
@@ -18,6 +47,8 @@ void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head 


	hpfs_lock_assert(s);



	hpfs_prefetch_sectors(s, secno, ahead);



	cond_resched();



	*bhp = bh = sb_bread(s, secno);
@@ -67,6 +98,8 @@ void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffe 
		return NULL;

	}



	hpfs_prefetch_sectors(s, secno, 4 + ahead);



	qbh->data = data = kmalloc(2048, GFP_NOFS);

	if (!data) {

		printk("HPFS: hpfs_map_4sectors: out of memory\n");

fs/hpfs/hpfs_fn.h

+5 −2
Original line number Diff line number Diff line
@@ -27,8 +27,9 @@ 
#define ALLOC_FWD_MAX	128

#define ALLOC_M		1

#define FNODE_RD_AHEAD	16

#define ANODE_RD_AHEAD	16

#define DNODE_RD_AHEAD	4

#define ANODE_RD_AHEAD	0

#define DNODE_RD_AHEAD	72

#define COUNT_RD_AHEAD	62



#define FREE_DNODES_ADD	58

#define FREE_DNODES_DEL	29
@@ -207,6 +208,7 @@ void hpfs_remove_fnode(struct super_block *, fnode_secno fno); 


/* buffer.c */



void hpfs_prefetch_sectors(struct super_block *, unsigned, int);

void *hpfs_map_sector(struct super_block *, unsigned, struct buffer_head **, int);

void *hpfs_get_sector(struct super_block *, unsigned, struct buffer_head **);

void *hpfs_map_4sectors(struct super_block *, unsigned, struct quad_buffer_head *, int);
@@ -271,6 +273,7 @@ void hpfs_evict_inode(struct inode *); 


__le32 *hpfs_map_dnode_bitmap(struct super_block *, struct quad_buffer_head *);

__le32 *hpfs_map_bitmap(struct super_block *, unsigned, struct quad_buffer_head *, char *);

void hpfs_prefetch_bitmap(struct super_block *, unsigned);

unsigned char *hpfs_load_code_page(struct super_block *, secno);

__le32 *hpfs_load_bitmap_directory(struct super_block *, secno bmp);

struct fnode *hpfs_map_fnode(struct super_block *s, ino_t, struct buffer_head **);

fs/hpfs/map.c

+18 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block, 
			 struct quad_buffer_head *qbh, char *id)

{

	secno sec;

	__le32 *ret;

	unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;

	if (hpfs_sb(s)->sb_chk) if (bmp_block >= n_bands) {

		hpfs_error(s, "hpfs_map_bitmap called with bad parameter: %08x at %s", bmp_block, id);
@@ -27,7 +28,23 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block, 
		hpfs_error(s, "invalid bitmap block pointer %08x -> %08x at %s", bmp_block, sec, id);

		return NULL;

	}

	return hpfs_map_4sectors(s, sec, qbh, 4);

	ret = hpfs_map_4sectors(s, sec, qbh, 4);

	if (ret) hpfs_prefetch_bitmap(s, bmp_block + 1);

	return ret;

}



void hpfs_prefetch_bitmap(struct super_block *s, unsigned bmp_block)

{

	unsigned to_prefetch, next_prefetch;

	unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;

	if (unlikely(bmp_block >= n_bands))

		return;

	to_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block]);

	if (unlikely(bmp_block + 1 >= n_bands))

		next_prefetch = 0;

	else

		next_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block + 1]);

	hpfs_prefetch_sectors(s, to_prefetch, 4 + 4 * (to_prefetch + 4 == next_prefetch));

}



/*

fs/hpfs/super.c

+7 −2
Original line number Diff line number Diff line
@@ -121,7 +121,7 @@ unsigned hpfs_count_one_bitmap(struct super_block *s, secno secno) 
	unsigned long *bits;

	unsigned count;



	bits = hpfs_map_4sectors(s, secno, &qbh, 4);

	bits = hpfs_map_4sectors(s, secno, &qbh, 0);

	if (!bits)

		return 0;

	count = bitmap_weight(bits, 2048 * BITS_PER_BYTE);
@@ -134,8 +134,13 @@ static unsigned count_bitmaps(struct super_block *s) 
	unsigned n, count, n_bands;

	n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;

	count = 0;

	for (n = 0; n < n_bands; n++)

	for (n = 0; n < COUNT_RD_AHEAD; n++) {

		hpfs_prefetch_bitmap(s, n);

	}

	for (n = 0; n < n_bands; n++) {

		hpfs_prefetch_bitmap(s, n + COUNT_RD_AHEAD);

		count += hpfs_count_one_bitmap(s, le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[n]));

	}

	return count;

}