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Message-ID: <alpine.LFD.2.00.1102101146470.3320@dhcp-27-109.brq.redhat.com>
Date: Thu, 10 Feb 2011 12:25:11 +0100 (CET)
From: Lukas Czerner <lczerner@...hat.com>
To: Tao Ma <tm@....ma>
cc: linux-ext4@...r.kernel.org,
Andreas Dilger <adilger.kernel@...ger.ca>,
Lukas Czerner <lczerner@...hat.com>
Subject: Re: [PATCH 4/4 v2] ext4: Speed up FITRIM by recording flags in
ext4_group_info.
On Thu, 10 Feb 2011, Tao Ma wrote:
> From: Tao Ma <boyu.mt@...bao.com>
>
> 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@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m4.039s
> user 0m0.000s
> sys 0m1.020s
> [root@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m3.577s
> user 0m0.001s
> sys 0m1.004s
> [root@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m3.380s
> user 0m0.000s
> sys 0m0.991s
>
> with the patch:
> [root@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m3.466s
> user 0m0.000s
> sys 0m0.966s
> [root@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m0.001s
> user 0m0.000s
> sys 0m0.001s
> [root@...u-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.
>
> After I delete some big image files and re-run the trim,
> it is still much faster than iterating the whole disk.
> /dev/sdb2 108G 25G 78G 24% /mnt/ext4
>
> [root@...u-tm test]# time ./ftrim /mnt/ext4/a
> real 0m0.513s
> user 0m0.000s
> sys 0m0.069s
Great it looks really good.
>
> Cc: Andreas Dilger <adilger.kernel@...ger.ca>
> Cc: Lukas Czerner <lczerner@...hat.com>
> Signed-off-by: Tao Ma <boyu.mt@...bao.com>
> ---
> fs/ext4/ext4.h | 8 +++++++-
> fs/ext4/mballoc.c | 22 ++++++++++++++++++++++
> 2 files changed, 29 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 0c8d97b..1d59a63 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. */
> + u64 s_last_trim_minblks;
> };
>
> static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
> @@ -1970,10 +1973,13 @@ 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_HAS_BEEN_TRIMMED(grp) \
> + (test_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..c7aa094 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2687,6 +2687,16 @@ 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))
> + clear_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT,
> + &(db->bb_state));
> +
> 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 +4782,10 @@ 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)->s_last_trim_minblks)
> + goto out;
> +
> trace_ext4_trim_all_free(sb, group, start, max);
>
> while (start < max) {
> @@ -4804,6 +4818,11 @@ 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)
> + set_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT,
> + &(e4b->bd_info->bb_state));
> +out:
> ext4_unlock_group(sb, group);
>
> ext4_debug("trimmed %d blocks in the group %d\n",
> @@ -4892,6 +4911,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> }
> range->len = trimmed * sb->s_blocksize;
>
> + if (!ret)
> + EXT4_SB(sb)->s_last_trim_minblks = minlen;
> +
Since this is not protected by any lock, would not it race in case of
multiple FITRIM calls ?
> out:
> return ret;
> }
>
Thanks!
-Lukas
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