Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=9f966be8996f2829406324c68e4c67c2d64d864b
Commit: 9f966be8996f2829406324c68e4c67c2d64d864b
Parent: d52df2e2ea2d881b1439bbdec7f67c27e0f47941
Author: OGAWA Hirofumi <[EMAIL PROTECTED]>
AuthorDate: Tue Jan 8 15:32:41 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Jan 8 16:10:35 2008 -0800
fat: optimize fat_count_free_clusters()
On large partition, scanning the free clusters is very slow if users
doesn't use "usefree" option.
For optimizing it, this patch uses sb_breadahead() to read of FAT
sectors. On some user's 15GB partition, this patch improved it very
much (1min => 600ms).
The following is the result of 2GB partition on my machine.
without patch:
[EMAIL PROTECTED] (/)# time df -h > /dev/null
real 0m1.202s
user 0m0.000s
sys 0m0.440s
with patch:
[EMAIL PROTECTED] (/)# time df -h > /dev/null
real 0m0.378s
user 0m0.012s
sys 0m0.168s
Signed-off-by: OGAWA Hirofumi <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
fs/fat/fatent.c | 28 ++++++++++++++++++++++++++++
1 files changed, 28 insertions(+), 0 deletions(-)
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 2c1b73f..5fb3669 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -590,21 +590,49 @@ error:
EXPORT_SYMBOL_GPL(fat_free_clusters);
+/* 128kb is the whole sectors for FAT12 and FAT16 */
+#define FAT_READA_SIZE (128 * 1024)
+
+static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
+ unsigned long reada_blocks)
+{
+ struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+ sector_t blocknr;
+ int i, offset;
+
+ ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+
+ for (i = 0; i < reada_blocks; i++)
+ sb_breadahead(sb, blocknr + i);
+}
+
int fat_count_free_clusters(struct super_block *sb)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
struct fatent_operations *ops = sbi->fatent_ops;
struct fat_entry fatent;
+ unsigned long reada_blocks, reada_mask, cur_block;
int err = 0, free;
lock_fat(sbi);
if (sbi->free_clusters != -1)
goto out;
+ reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
+ reada_mask = reada_blocks - 1;
+ cur_block = 0;
+
free = 0;
fatent_init(&fatent);
fatent_set_entry(&fatent, FAT_START_ENT);
while (fatent.entry < sbi->max_cluster) {
+ /* readahead of fat blocks */
+ if ((cur_block & reada_mask) == 0) {
+ unsigned long rest = sbi->fat_length - cur_block;
+ fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
+ }
+ cur_block++;
+
err = fat_ent_read_block(sb, &fatent);
if (err)
goto out;
-
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