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");