On Mon, Apr 05, 2021 at 05:38:16PM +0800, Hu Weiwen wrote:
> Original implementation use insertion sort, and its time complexity is
> O(n^2). This patch use qsort instead. When I create a directory with
> 100k entries, this reduces the user space time from around 3 mins to
> 0.5s.
>
> Create such a large directory for benchmark with:
> mkdir large; cd large; touch $(seq 100000);
>
> Signed-off-by: Hu Weiwen <seh...@mail.scut.edu.cn>
This patch looks good to me, will test it later.
> ---
> lib/inode.c | 53 +++++++++++++++++++++++++++++++++--------------------
> 1 file changed, 33 insertions(+), 20 deletions(-)
>
> diff --git a/lib/inode.c b/lib/inode.c
> index d52facf..ef55e88 100644
> --- a/lib/inode.c
> +++ b/lib/inode.c
> @@ -96,21 +96,6 @@ unsigned int erofs_iput(struct erofs_inode *inode)
> return 0;
> }
>
> -static int dentry_add_sorted(struct erofs_dentry *d, struct list_head *head)
> -{
> - struct list_head *pos;
> -
> - list_for_each(pos, head) {
> - struct erofs_dentry *d2 =
> - container_of(pos, struct erofs_dentry, d_child);
> -
> - if (strcmp(d->name, d2->name) < 0)
> - break;
> - }
> - list_add_tail(&d->d_child, pos);
> - return 0;
> -}
> -
> struct erofs_dentry *erofs_d_alloc(struct erofs_inode *parent,
> const char *name)
> {
> @@ -122,7 +107,7 @@ struct erofs_dentry *erofs_d_alloc(struct erofs_inode
> *parent,
> strncpy(d->name, name, EROFS_NAME_LEN - 1);
> d->name[EROFS_NAME_LEN - 1] = '\0';
>
> - dentry_add_sorted(d, &parent->i_subdirs);
> + list_add_tail(&d->d_child, &parent->i_subdirs);
> return d;
> }
>
> @@ -156,10 +141,19 @@ static int __allocate_inode_bh_data(struct erofs_inode
> *inode,
> return 0;
> }
>
> +static int comp_subdir(const void *a, const void *b)
> +{
> + const struct erofs_dentry *da, *db;
> +
> + da = *((const struct erofs_dentry **)a);
> + db = *((const struct erofs_dentry **)b);
> + return strcmp(da->name, db->name);
> +}
> +
> -int erofs_prepare_dir_file(struct erofs_inode *dir)
> +int erofs_prepare_dir_file(struct erofs_inode *dir, unsigned int nr_subdirs)
> {
> - struct erofs_dentry *d;
> - unsigned int d_size, i_nlink;
> + struct erofs_dentry *d, *n, **sorted_d;
> + unsigned int d_size, i_nlink, i;
> int ret;
>
> /* dot is pointed to the current dir inode */
> @@ -172,6 +166,22 @@ int erofs_prepare_dir_file(struct erofs_inode *dir)
> d->inode = erofs_igrab(dir->i_parent);
> d->type = EROFS_FT_DIR;
>
> + /* sort subdirs */
> + nr_subdirs += 2;
> + sorted_d = malloc(nr_subdirs * sizeof(d));
> + if (!sorted_d)
> + return -ENOMEM;
> + i = 0;
> + list_for_each_entry_safe(d, n, &dir->i_subdirs, d_child) {
> + list_del(&d->d_child);
> + sorted_d[i++] = d;
> + }
> + DBG_BUGON(i != nr_subdirs);
> + qsort(sorted_d, nr_subdirs, sizeof(d), comp_subdir);
> + for (i = 0; i < nr_subdirs; i++)
> + list_add_tail(&sorted_d[i]->d_child, &dir->i_subdirs);
> + free(sorted_d);
> +
> /* let's calculate dir size and update i_nlink */
> d_size = 0;
> i_nlink = 0;
> @@ -922,6 +932,7 @@ struct erofs_inode *erofs_mkfs_build_tree(struct
> erofs_inode *dir)
> DIR *_dir;
> struct dirent *dp;
> struct erofs_dentry *d;
> + unsigned int nr_subdirs;
>
> ret = erofs_prepare_xattr_ibody(dir);
> if (ret < 0)
> @@ -961,6 +972,7 @@ struct erofs_inode *erofs_mkfs_build_tree(struct
> erofs_inode *dir)
> return ERR_PTR(-errno);
> }
>
> + nr_subdirs = 0;
> while (1) {
> /*
> * set errno to 0 before calling readdir() in order to
> @@ -984,6 +996,7 @@ struct erofs_inode *erofs_mkfs_build_tree(struct
> erofs_inode *dir)
> ret = PTR_ERR(d);
> goto err_closedir;
> }
> + nr_subdirs++;
>
> /* to count i_nlink for directories */
> d->type = (dp->d_type == DT_DIR ?
> @@ -996,7 +1009,7 @@ struct erofs_inode *erofs_mkfs_build_tree(struct
> erofs_inode *dir)
> }
> closedir(_dir);
>
> - ret = erofs_prepare_dir_file(dir);
> + ret = erofs_prepare_dir_file(dir, nr_subdirs);
> if (ret)
> goto err;
>
> --
> 2.25.1
>
