Re: Fwd: Fwd: VFAT performance.

OGAWA Hirofumi
2003-06-05T17:41:09Z

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Rogier Wolff <R.E.Wolff@BitWizard.nl> writes:

> The way to fix this would be to be able to assign a higher cache
> priority (*) to the blocks in the FAT, and to read more than just 4k
> per seek to the FAT.

I tried it by attached *stupid* patch.

copying 500M data

root@devron (x)[1014]# time dd if=/dev/hda6 bs=1M count=500 > /dev/null
500+0 records in
500+0 records out
524288000 bytes transferred in 44.988916 seconds (11653715 bytes/sec)

real 0m45.011s
user 0m0.008s
sys 0m8.723s

2.5.70-bk9
root@devron (a)[1032]# time dd if=file bs=1M count=500 > /dev/null
500+0 records in
500+0 records out
524288000 bytes transferred in 75.510951 seconds (6943205 bytes/sec)

real 1m15.538s
user 0m0.015s
sys 0m16.493s

2.5.70-bk9+patch
root@devron (a)[1024]# time dd if=file bs=1M count=500 > /dev/null
500+0 records in
500+0 records out
524288000 bytes transferred in 52.034399 seconds (10075796 bytes/sec)

real 0m52.041s
user 0m0.006s
sys 0m17.594s

You're right. It seems that that optimization has sufficient effect to
non fragment file. Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

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fs/fat/cache.c | 22 +++++++++++++++++-----
fs/fat/inode.c | 4 +++-
include/linux/msdos_fs_sb.h | 1 +
3 files changed, 21 insertions(+), 6 deletions(-)

diff -puN fs/fat/cache.c~fat_test fs/fat/cache.c
--- linux-2.5.70/fs/fat/cache.c~fat_test 2003-06-06 01:51:46.000000000 +0900
+++ linux-2.5.70-hirofumi/fs/fat/cache.c 2003-06-06 02:14:49.000000000 +0900
@@ -17,7 +17,7 @@ int __fat_access(struct super_block *sb,
struct msdos_sb_info *sbi = MSDOS_SB(sb);
struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
unsigned char *p_first, *p_last;
- int copy, first, last, next, b;
+ int copy, first, last, next, b, i;

if (sbi->fat_bits == 32) {
first = last = nr*4;
@@ -28,10 +28,22 @@ int __fat_access(struct super_block *sb,
last = first+1;
}
b = sbi->fat_start + (first >> sb->s_blocksize_bits);
- if (!(bh = sb_bread(sb, b))) {
- printk(KERN_ERR "FAT: bread(block %d) in"
- " fat_access failed\n", b);
- return -EIO;
+ bh = NULL;
+ for (i = 0; i < 16; i++) {
+ if (sbi->fat_bh[i]->b_blocknr == b) {
+ bh = sbi->fat_bh[i];
+ break;
+ }
+ }
+ if (bh == NULL) {
+ for (i = 0; i < 16; i++) {
+ brelse(sbi->fat_bh[i]);
+ sbi->fat_bh[i] = sb_bread(sb, b + i);
+ if (sbi->fat_bh[i] == NULL)
+ return -EIO;
+ get_bh(sbi->fat_bh[i]);
+ }
+ bh = sbi->fat_bh[0];
}
if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
bh2 = bh;
diff -puN fs/fat/inode.c~fat_test fs/fat/inode.c
--- linux-2.5.70/fs/fat/inode.c~fat_test 2003-06-06 01:52:44.000000000 +0900
+++ linux-2.5.70-hirofumi/fs/fat/inode.c 2003-06-06 02:12:45.000000000 +0900
@@ -158,7 +158,9 @@ void fat_clear_inode(struct inode *inode
void fat_put_super(struct super_block *sb)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
-
+ int i;
+ for (i = 0; i < 16; i++)
+ brelse(sbi->fat_bh[i]);
fat_clusters_flush(sb);
if (sbi->nls_disk) {
unload_nls(sbi->nls_disk);
diff -puN include/linux/msdos_fs_sb.h~fat_test include/linux/msdos_fs_sb.h
--- linux-2.5.70/include/linux/msdos_fs_sb.h~fat_test 2003-06-06 01:53:11.000000000 +0900
+++ linux-2.5.70-hirofumi/include/linux/msdos_fs_sb.h 2003-06-06 02:01:55.000000000 +0900
@@ -59,6 +59,7 @@ struct msdos_sb_info {

spinlock_t cache_lock;
struct fat_cache cache_array[FAT_CACHE_NR], *cache;
+ struct buffer_head *fat_bh[16];
};

#endif

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