Commit 3d56b8d2 authored by Tao Ma's avatar Tao Ma Committed by Theodore Ts'o
Browse files

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/sdb1              40G   21G   17G  56% /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 linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m5.505s
user	0m0.000s
sys	0m1.224s
[root@boyu-tm linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m5.359s
user	0m0.000s
sys	0m1.178s
[root@boyu-tm linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m5.228s
user	0m0.000s
sys	0m1.151s

with the patch:
[root@boyu-tm linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m5.625s
user	0m0.000s
sys	0m1.269s
[root@boyu-tm linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m0.002s
user	0m0.000s
sys	0m0.001s
[root@boyu-tm linux-2.6]# time ./ftrim /mnt/ext4/a
real	0m0.002s
user	0m0.000s
sys	0m0.001s

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.

[root@boyu-tm test]# time ./ftrim /mnt/ext4/a
real	0m1.217s
user	0m0.000s
sys	0m0.196s

Cc: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: default avatarAndreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: default avatarTao Ma <boyu.mt@taobao.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent b3d4c2b1

fs/ext4/ext4.h

+12 −1
Original line number Diff line number Diff line
@@ -1215,6 +1215,9 @@ struct ext4_sb_info { 


	/* Kernel thread for multiple mount protection */

	struct task_struct *s_mmp_tsk;



	/* 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)
@@ -2081,10 +2084,18 @@ struct ext4_group_info { 
};



#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

fs/ext4/mballoc.c

+20 −0
Original line number Diff line number Diff line
@@ -2628,6 +2628,15 @@ 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()
@@ -4838,6 +4847,10 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group, 
	bitmap = e4b.bd_bitmap;



	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;



	start = (e4b.bd_info->bb_first_free > start) ?

		e4b.bd_info->bb_first_free : start;
@@ -4869,6 +4882,10 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group, 
		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_mb_unload_buddy(&e4b);
@@ -4957,6 +4974,9 @@ 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;

}

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