Re: [PATCH 2/2] f2fs: speed up shrinking extent tree entries

[Jaegeuk Kim <jaegeuk@kernel.org>]

On Mon, Dec 21, 2015 at 07:38:41PM -0800, Jaegeuk Kim wrote:
> If there is no candidates for shrinking slab entries, we don't need to traverse
> any trees at all.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/extent_cache.c | 12 ++++++++++++
>  fs/f2fs/f2fs.h         |  1 +
>  fs/f2fs/shrinker.c     |  2 +-
>  3 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
> index 0e97d6af..32693af 100644
> --- a/fs/f2fs/extent_cache.c
> +++ b/fs/f2fs/extent_cache.c
> @@ -71,6 +71,8 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode)
>  		atomic_set(&et->refcount, 0);
>  		et->count = 0;
>  		atomic_inc(&sbi->total_ext_tree);
> +	} else {
> +		atomic_dec(&sbi->total_zombie_tree);
>  	}
>  	atomic_inc(&et->refcount);
>  	up_write(&sbi->extent_tree_lock);
> @@ -547,10 +549,14 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
>  	unsigned int found;
>  	unsigned int node_cnt = 0, tree_cnt = 0;
>  	int remained;
> +	bool do_free = false;
>  
>  	if (!test_opt(sbi, EXTENT_CACHE))
>  		return 0;
>  
> +	if (!atomic_read(&sbi->total_zombie_tree))
> +		goto free_node;
> +
>  	if (!down_write_trylock(&sbi->extent_tree_lock))
>  		goto out;
>  
> @@ -580,6 +586,7 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
>  	}
>  	up_write(&sbi->extent_tree_lock);
>  
> +free_node:
>  	/* 2. remove LRU extent entries */
>  	if (!down_write_trylock(&sbi->extent_tree_lock))
>  		goto out;
> @@ -591,9 +598,13 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
>  		if (!remained--)
>  			break;
>  		list_del_init(&en->list);
> +		do_free = true;
>  	}
>  	spin_unlock(&sbi->extent_lock);
>  
> +	if (do_free == false)
> +		goto unlock_out;
> +
>  	/*
>  	 * reset ino for searching victims from beginning of global extent tree.
>  	 */
> @@ -651,6 +662,7 @@ void f2fs_destroy_extent_tree(struct inode *inode)
>  
>  	if (inode->i_nlink && !is_bad_inode(inode) && et->count) {
>  		atomic_dec(&et->refcount);
> +		atomic_dec(&sbi->total_zombie_tree);

This will be changed to atomic_inc().
Sorry for confusion.

Thanks,

>  		return;
>  	}
>  
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index a7f6191..90fb970 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -763,6 +763,7 @@ struct f2fs_sb_info {
>  	struct list_head extent_list;		/* lru list for shrinker */
>  	spinlock_t extent_lock;			/* locking extent lru list */
>  	atomic_t total_ext_tree;		/* extent tree count */
> +	atomic_t total_zombie_tree;		/* extent zombie tree count */
>  	atomic_t total_ext_node;		/* extent info count */
>  
>  	/* basic filesystem units */
> diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
> index a11e099..93606f2 100644
> --- a/fs/f2fs/shrinker.c
> +++ b/fs/f2fs/shrinker.c
> @@ -32,7 +32,7 @@ static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
>  
>  static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
>  {
> -	return atomic_read(&sbi->total_ext_tree) +
> +	return atomic_read(&sbi->total_zombie_tree) +
>  				atomic_read(&sbi->total_ext_node);
>  }
>  
> -- 
> 2.5.4 (Apple Git-61)