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: Mikulas Patocka <mpatocka@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/hpfs/buffer.c b/fs/hpfs/buffer.c
index f49d149..4d0a1af 100644
--- a/fs/hpfs/buffer.c
+++ b/fs/hpfs/buffer.c
@@ -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 @@
hpfs_lock_assert(s);
+ hpfs_prefetch_sectors(s, secno, ahead);
+
cond_resched();
*bhp = bh = sb_bread(s, secno);
@@ -67,6 +98,8 @@
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");
diff --git a/fs/hpfs/hpfs_fn.h b/fs/hpfs/hpfs_fn.h
index b7ae286..1b39863 100644
--- a/fs/hpfs/hpfs_fn.h
+++ b/fs/hpfs/hpfs_fn.h
@@ -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 @@
/* 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 @@
__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 **);
diff --git a/fs/hpfs/map.c b/fs/hpfs/map.c
index 803d3da..3aa66ae 100644
--- a/fs/hpfs/map.c
+++ b/fs/hpfs/map.c
@@ -17,6 +17,7 @@
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 @@
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));
}
/*
diff --git a/fs/hpfs/super.c b/fs/hpfs/super.c
index 962e90c..4334cda 100644
--- a/fs/hpfs/super.c
+++ b/fs/hpfs/super.c
@@ -121,7 +121,7 @@
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 @@
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;
}