Re: [RFC PATHC 1/2] f2fs: apply write hints to select the type of segments for buffered write

[Chao Yu]

On 2017/11/9 13:51, Hyunchul Lee wrote:
> From: Hyunchul Lee <cheol.lee@xxxxxxx>
> 
> Write hints helps F2FS to determine which type of segments would be
> selected for buffered write.
> 
> This patch implements the mapping from write hints to segment types
> as shown below.
> 
>   hints               segment type
>   -----               ------------
>   WRITE_LIFE_SHORT    CURSEG_COLD_DATA
>   WRITE_LIFE_EXTREME  CURSEG_HOT_DATA

Should keep consistent with code implementation.

	WRITE_LIFE_SHORT    CURSEG_HOT_DATA
	WRITE_LIFE_EXTREME  CURSEG_COLD_DATA

>   others              CURSEG_WARM_DATA
> 
> the F2FS poliy for hot/cold seperation has precedence over this hints.
> And hints are not applied in in-place update.
> 
> Signed-off-by: Hyunchul Lee <cheol.lee@xxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,

> ---
>  fs/f2fs/segment.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index c695ff4..45aef53 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2258,6 +2258,18 @@ static bool __has_curseg_space(struct f2fs_sb_info *sbi, int type)
>  	return false;
>  }
>  
> +int rw_hint_to_seg_type(enum rw_hint hint)
> +{
> +	switch (hint) {
> +	case WRITE_LIFE_SHORT:
> +		return CURSEG_HOT_DATA;
> +	case WRITE_LIFE_EXTREME:
> +		return CURSEG_COLD_DATA;
> +	default:
> +		return CURSEG_WARM_DATA;
> +	}
> +}
> +
>  static int __get_segment_type_2(struct f2fs_io_info *fio)
>  {
>  	if (fio->type == DATA)
> @@ -2292,7 +2304,7 @@ static int __get_segment_type_6(struct f2fs_io_info *fio)
>  			return CURSEG_COLD_DATA;
>  		if (is_inode_flag_set(inode, FI_HOT_DATA))
>  			return CURSEG_HOT_DATA;
> -		return CURSEG_WARM_DATA;
> +		return rw_hint_to_seg_type(inode->i_write_hint);
>  	} else {
>  		if (IS_DNODE(fio->page))
>  			return is_cold_node(fio->page) ? CURSEG_WARM_NODE :
>