Hi Lukas,
On 02/09/2011 10:01 PM, Lukas Czerner wrote:
On Wed, 9 Feb 2011, Tao Ma wrote:
From: Tao Ma<boyu.mt@xxxxxxxxxx>
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. The idea
is inspired by Andreas and Lukas Czerner.
Hi Tao,
This is great, thanks for the patch! Do you have any benchmark numbers
showing how much does it improve FSTRIM time ? It seems it might help a
lot. Couple of comments bellow.
<snip>
@@ -4772,6 +4785,10 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
ext4_lock_group(sb, group);
+ if (EXT4_MB_GRP_HAS_BEEN_TRIMMED(e4b->bd_info)&&
+ minblocks>= EXT4_SB(sb)->trim_minlen)
+ goto out;
+
I think this can be placed in the ext4_trim_fs() in the for() loop so we can
avoid unnecessary call to ext4_trim_all_free.
I remembered why I put the check here. We have to check this flag with
the group locked. So in ext4_trim_fs, we don't lock the group and it is
unsafe to check it there since we may free some blocks and clear the bit
in the same time in release_blocks_on_commit.
Regards,
Tao
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