提交 275f495d 编写于 作者: M Mikulas Patocka 提交者: Linus Torvalds

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: NMikulas Patocka <mpatocka@artax.karlin.mff.cuni.cz>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
上级 a0c1b759
......@@ -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");
......
......@@ -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 **);
......
......@@ -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));
}
/*
......
......@@ -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;
}
......
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