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: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7aa4c16..73c2540 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2628,6 +2628,15 @@
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 @@
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 @@
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 @@
}
range->len = trimmed * sb->s_blocksize;
+ if (!ret)
+ atomic_set(&EXT4_SB(sb)->s_last_trim_minblks, minlen);
+
out:
return ret;
}