Re: [f2fs-dev] [RFC PATCH] f2fs: do not use CURSEG_ALL_DATA_ATGC in foreground or urgent GC

[Chao Yu <yuchao0@huawei.com>]

On 2021/3/16 21:15, Weichao Guo via Linux-f2fs-devel wrote:
> CURSEG_ALL_DATA_ATGC is introduced by age threshold based GC for better
> hot/cold data seperation and avoiding free segment cost. However, LFS
> write mode is preferred in the scenario of foreground or urgent GC, which
> should be finished ASAP. So, let's only use CURSEG_ALL_DATA_ATGC when not
> urgent in background GC.

Weichao,

select_gc_type()

	case GC_URGENT_HIGH:
		gc_mode = GC_GREEDY;

We have selected 'greedy' algorithm rather than 'atgc' algorithm for high
urgent gc, did you mean we should use 'greedy' for low urgent gc as well?

Thanks,

> 
> Signed-off-by: Weichao Guo <guoweichao@oppo.com>
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> ---
>   fs/f2fs/gc.c      | 3 ++-
>   fs/f2fs/segment.c | 4 +++-
>   2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 86ba8ed..ee42f6e 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1120,7 +1120,8 @@ static int move_data_block(struct inode *inode, block_t bidx,
>   	block_t newaddr;
>   	int err = 0;
>   	bool lfs_mode = f2fs_lfs_mode(fio.sbi);
> -	int type = fio.sbi->am.atgc_enabled ?
> +	int type = fio.sbi->am.atgc_enabled && gc_type == BG_GC &&
> +				fio.sbi->gc_mode < GC_URGENT_HIGH ?
>   				CURSEG_ALL_DATA_ATGC : CURSEG_COLD_DATA;
>   
>   	/* do not read out */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 32b915e..cbfb0d1 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3264,7 +3264,9 @@ static int __get_segment_type_6(struct f2fs_io_info *fio)
>   		struct inode *inode = fio->page->mapping->host;
>   
>   		if (is_cold_data(fio->page)) {
> -			if (fio->sbi->am.atgc_enabled)
> +			if (fio->sbi->am.atgc_enabled &&
> +				fio->io_type == FS_DATA_IO &&
> +				fio->sbi->gc_mode < GC_URGENT_HIGH)
>   				return CURSEG_ALL_DATA_ATGC;
>   			else
>   				return CURSEG_COLD_DATA;
> 


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