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Date: Thu, 3 Nov 2022 21:51:04 +0900
From: "Sungjong Seo" <sj1557.seo@...sung.com>
To: "'Namjae Jeon'" <linkinjeon@...nel.org>
Cc: "'linux-kernel'" <linux-kernel@...r.kernel.org>,
"'linux-fsdevel'" <linux-fsdevel@...r.kernel.org>,
<sj1557.seo@...sung.com>
Subject: RE: [PATCH v2 2/2] exfat: hint the empty entry which at the end of
cluster chain
> After traversing all directory entries, hint the empty directory
> entry no matter whether or not there are enough empty directory
> entries.
>
> After this commit, hint the empty directory entries like this:
>
> 1. Hint the deleted directory entries if enough;
> 2. Hint the deleted and unused directory entries which at the
> end of the cluster chain no matter whether enough or not(Add
> by this commit);
> 3. If no any empty directory entries, hint the empty directory
> entries in the new cluster(Add by this commit).
>
> This avoids repeated traversal of directory entries, reduces CPU
> usage, and improves the performance of creating files and
> directories(especially on low-performance CPUs).
>
> Test create 5000 files in a class 4 SD card on imx6q-sabrelite
> with:
>
> for ((i=0;i<5;i++)); do
> sync
> time (for ((j=1;j<=1000;j++)); do touch file$((i*1000+j)); done)
> done
>
> The more files, the more performance improvements.
>
> Before After Improvement
> 1~1000 25.360s 22.168s 14.40%
> 1001~2000 38.242s 28.72ss 33.15%
> 2001~3000 49.134s 35.037s 40.23%
> 3001~4000 62.042s 41.624s 49.05%
> 4001~5000 73.629s 46.772s 57.42%
>
> Signed-off-by: Yuezhang Mo <Yuezhang.Mo@...y.com>
> Reviewed-by: Andy Wu <Andy.Wu@...y.com>
> Reviewed-by: Aoyama Wataru <wataru.aoyama@...y.com>
Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>
Looks good. Thanks!
> ---
> fs/exfat/dir.c | 26 ++++++++++++++++++++++----
> fs/exfat/namei.c | 33 +++++++++++++++++++++------------
> 2 files changed, 43 insertions(+), 16 deletions(-)
>
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
> index 9f9b8435baca..5497a610808d 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -905,17 +905,24 @@ static inline void exfat_reset_empty_hint(struct
> exfat_hint_femp *hint_femp)
>
> static inline void exfat_set_empty_hint(struct exfat_inode_info *ei,
> struct exfat_hint_femp *candi_empty, struct exfat_chain *clu,
> - int dentry, int num_entries)
> + int dentry, int num_entries, int entry_type)
> {
> if (ei->hint_femp.eidx == EXFAT_HINT_NONE ||
> ei->hint_femp.eidx > dentry) {
> + int total_entries = EXFAT_B_TO_DEN(i_size_read(&ei-
> >vfs_inode));
> +
> if (candi_empty->count == 0) {
> candi_empty->cur = *clu;
> candi_empty->eidx = dentry;
> }
>
> - candi_empty->count++;
> - if (candi_empty->count == num_entries)
> + if (entry_type == TYPE_UNUSED)
> + candi_empty->count += total_entries - dentry;
> + else
> + candi_empty->count++;
> +
> + if (candi_empty->count == num_entries ||
> + candi_empty->count + candi_empty->eidx == total_entries)
> ei->hint_femp = *candi_empty;
> }
> }
> @@ -989,7 +996,8 @@ int exfat_find_dir_entry(struct super_block *sb,
> struct exfat_inode_info *ei,
> step = DIRENT_STEP_FILE;
>
> exfat_set_empty_hint(ei, &candi_empty, &clu,
> - dentry, num_entries);
> + dentry, num_entries,
> + entry_type);
>
> brelse(bh);
> if (entry_type == TYPE_UNUSED)
> @@ -1100,6 +1108,16 @@ int exfat_find_dir_entry(struct super_block *sb,
> struct exfat_inode_info *ei,
> goto rewind;
> }
>
> + /*
> + * set the EXFAT_EOF_CLUSTER flag to avoid search
> + * from the beginning again when allocated a new cluster
> + */
> + if (ei->hint_femp.eidx == EXFAT_HINT_NONE) {
> + ei->hint_femp.cur.dir = EXFAT_EOF_CLUSTER;
> + ei->hint_femp.eidx = p_dir->size * dentries_per_clu;
> + ei->hint_femp.count = 0;
> + }
> +
> /* initialized hint_stat */
> hint_stat->clu = p_dir->dir;
> hint_stat->eidx = 0;
> diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
> index b617bebc3d0f..add4893711d3 100644
> --- a/fs/exfat/namei.c
> +++ b/fs/exfat/namei.c
> @@ -224,11 +224,18 @@ static int exfat_search_empty_slot(struct
> super_block *sb,
>
> if (hint_femp->eidx != EXFAT_HINT_NONE) {
> dentry = hint_femp->eidx;
> - if (num_entries <= hint_femp->count) {
> - hint_femp->eidx = EXFAT_HINT_NONE;
> - return dentry;
> - }
>
> + /*
> + * If hint_femp->count is enough, it is needed to check if
> + * there are actual empty entries.
> + * Otherwise, and if "dentry + hint_famp->count" is also
> equal
> + * to "p_dir->size * dentries_per_clu", it means ENOSPC.
> + */
> + if (dentry + hint_femp->count == p_dir->size *
> dentries_per_clu
> + && num_entries > hint_femp->count)
> + return -ENOSPC;
> +
> + hint_femp->eidx = EXFAT_HINT_NONE;
> exfat_chain_dup(&clu, &hint_femp->cur);
> } else {
> exfat_chain_dup(&clu, p_dir);
> @@ -293,6 +300,12 @@ static int exfat_search_empty_slot(struct super_block
> *sb,
> }
> }
>
> + hint_femp->eidx = p_dir->size * dentries_per_clu - num_empty;
> + hint_femp->count = num_empty;
> + if (num_empty == 0)
> + exfat_chain_set(&hint_femp->cur, EXFAT_EOF_CLUSTER, 0,
> + clu.flags);
> +
> return -ENOSPC;
> }
>
> @@ -369,15 +382,11 @@ static int exfat_find_empty_entry(struct inode
> *inode,
> if (exfat_ent_set(sb, last_clu, clu.dir))
> return -EIO;
>
> - if (hint_femp.eidx == EXFAT_HINT_NONE) {
> - /* the special case that new dentry
> - * should be allocated from the start of new cluster
> - */
> - hint_femp.eidx = EXFAT_B_TO_DEN_IDX(p_dir->size, sbi);
> - hint_femp.count = sbi->dentries_per_clu;
> -
> + if (hint_femp.cur.dir == EXFAT_EOF_CLUSTER)
> exfat_chain_set(&hint_femp.cur, clu.dir, 0, clu.flags);
> - }
> +
> + hint_femp.count += sbi->dentries_per_clu;
> +
> hint_femp.cur.size++;
> p_dir->size++;
> size = EXFAT_CLU_TO_B(p_dir->size, sbi);
> --
> 2.25.1
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