by Tao Ma

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Subject: [PATCH 4/4 V3] ext4: Speed up FITRIM by recording flags in ext4_group_info.

changlog from v2 -> v3:
change s_last_trim_minblks from u64 to atomic_t to avoid a race.

Regards,
Tao

>From 3875493dea3cc25be5460c175267f08a7ed540bc Mon Sep 17 00:00:00 2001
From: Tao Ma <[email protected]>
Date: Fri, 25 Feb 2011 06:10:26 +0800
Subject: [PATCH 4/4 V3] ext4: Speed up FITRIM by recording flags in ext4_group_info.

In ext4, when FITRIM is called every time, we iterate all the
groups and do trim one by one. It is a bit time wasting if the
group has been trimmed and there is no change since the last
trim.

So this patch adds a new flag in ext4_group_info->bb_state to
indicate that the group has been trimmed, and it will be cleared
if some blocks is freed(in release_blocks_on_commit). Another
trim_minlen is added in ext4_sb_info to record the last minlen
we use to trim the volume, so that if the caller provide a small
one, we will go on the trim regardless of the bb_state.

A simple test with my intel x25m ssd:
df -h shows:
/dev/sdb2 108G 35G 68G 34% /mnt/ext4
Block size: 4096

run the FITRIM with the following parameter:
range.start = 0;
range.len = UINT64_MAX;
range.minlen = 1048576;

without the patch:
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m4.039s
user 0m0.000s
sys 0m1.020s
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m3.577s
user 0m0.001s
sys 0m1.004s
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m3.380s
user 0m0.000s
sys 0m0.991s

with the patch:
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m3.466s
user 0m0.000s
sys 0m0.966s
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m0.001s
user 0m0.000s
sys 0m0.001s
[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m0.001s
user 0m0.000s
sys 0m0.000s

A big improvement for the 2nd and 3rd run.

Even after I delete some big image files, it is still much
faster than iterating the whole disk.
/dev/sdb2 108G 25G 78G 24% /mnt/ext4

[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real 0m0.513s
user 0m0.000s
sys 0m0.069s

Cc: Lukas Czerner <[email protected]>
Reviewed-by: Andreas Dilger <[email protected]>
Signed-off-by: Tao Ma <[email protected]>
---
fs/ext4/ext4.h | 13 ++++++++++++-
fs/ext4/mballoc.c | 20 ++++++++++++++++++++
fs/ext4/super.c | 2 ++
3 files changed, 34 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0c8d97b..715c0a4 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1200,6 +1200,9 @@ struct ext4_sb_info {
struct ext4_li_request *s_li_request;
/* Wait multiplier for lazy initialization thread */
unsigned int s_li_wait_mult;
+
+ /* record the last minlen when FITRIM is called. */
+ atomic_t s_last_trim_minblks;
};

static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
@@ -1970,11 +1973,19 @@ struct ext4_group_info {
* 5 free 8-block regions. */
};

-#define EXT4_GROUP_INFO_NEED_INIT_BIT 0
+#define EXT4_GROUP_INFO_NEED_INIT_BIT 0
+#define EXT4_GROUP_INFO_WAS_TRIMMED_BIT 1

#define EXT4_MB_GRP_NEED_INIT(grp) \
(test_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &((grp)->bb_state)))

+#define EXT4_MB_GRP_WAS_TRIMMED(grp) \
+ (test_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
+#define EXT4_MB_GRP_SET_TRIMMED(grp) \
+ (set_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
+#define EXT4_MB_GRP_CLEAR_TRIMMED(grp) \
+ (clear_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
+
#define EXT4_MAX_CONTENTION 8
#define EXT4_CONTENTION_THRESHOLD 2

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4eadac8..29d7d17 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2687,6 +2687,15 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
rb_erase(&entry->node, &(db->bb_free_root));
mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);

+ /*
+ * Clear the trimmed flag for the group so that the next
+ * ext4_trim_fs can trim it.
+ * If the volume is mounted with -o discard, online discard
+ * is supported and the free blocks will be trimmed online.
+ */
+ if (!test_opt(sb, DISCARD))
+ EXT4_MB_GRP_CLEAR_TRIMMED(db);
+
if (!db->bb_free_root.rb_node) {
/* No more items in the per group rb tree
* balance refcounts from ext4_mb_free_metadata()
@@ -4772,6 +4781,10 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,

ext4_lock_group(sb, group);

+ if (EXT4_MB_GRP_WAS_TRIMMED(e4b->bd_info) &&
+ minblocks >= atomic_read(&EXT4_SB(sb)->s_last_trim_minblks))
+ goto out;
+
trace_ext4_trim_all_free(sb, group, start, max);

while (start < max) {
@@ -4804,6 +4817,10 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
if ((e4b->bd_info->bb_free - free_count) < minblocks)
break;
}
+
+ if (!ret)
+ EXT4_MB_GRP_SET_TRIMMED(e4b->bd_info);
+out:
ext4_unlock_group(sb, group);

ext4_debug("trimmed %d blocks in the group %d\n",
@@ -4892,6 +4909,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
}
range->len = trimmed * sb->s_blocksize;

+ if (!ret)
+ atomic_set(&EXT4_SB(sb)->s_last_trim_minblks, minlen);
+
out:
return ret;
}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4898cb1..0fa3ed6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3045,6 +3045,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_sectors_written_start =
part_stat_read(sb->s_bdev->bd_part, sectors[1]);

+ atomic_set(&sbi->s_last_trim_minblks, 0);
+
/* Cleanup superblock name */
for (cp = sb->s_id; (cp = strchr(cp, '/'));)
*cp = '!';
--
1.6.3.GIT