Re: [PATCH] f2fs: fix to avoid use GC_AT when setting gc_mode as GC_URGENT_MID

[Chao Yu]

On 2024/10/22 17:14, Zhiguo Niu wrote:
> GC_URGENT_MID is introduced by commit
> d98af5f45520 ("f2fs: introduce gc_urgent_mid mode"), aim to does GC
> forcibly uses cost benefit GC approach, but if ATGC is enabled at
> the same time, Age-threshold approach will be selected, which can only
> do amount of GC and it is much less than the numbers of CB approach.

gc urgent low(2): lowers the bar of checking I/O idling in
		  order to process outstanding discard commands and GC a
		  little bit aggressively. uses cost benefit GC approach.

GC_URGENT_LOW uses CB algorithm as well?

Thanks,

> some traces:
>    f2fs_gc-254:48-396     [007] ..... 2311600.684028: f2fs_gc_begin: dev = (254,48), gc_type = Background GC, no_background_GC = 0, nr_free_secs = 0, nodes = 1053, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0
>    f2fs_gc-254:48-396     [007] ..... 2311600.684527: f2fs_get_victim: dev = (254,48), type = No TYPE, policy = (Background GC, LFS-mode, Age-threshold), victim = 10, cost = 4294364975, ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 44898
>    f2fs_gc-254:48-396     [007] ..... 2311600.714835: f2fs_gc_end: dev = (254,48), ret = 0, seg_freed = 0, sec_freed = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0
>    f2fs_gc-254:48-396     [007] ..... 2311600.714843: f2fs_background_gc: dev = (254,48), wait_ms = 50, prefree = 0, free = 44898
>    f2fs_gc-254:48-396     [007] ..... 2311600.771785: f2fs_gc_begin: dev = (254,48), gc_type = Background GC, no_background_GC = 0, nr_free_secs = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:
>    f2fs_gc-254:48-396     [007] ..... 2311600.772275: f2fs_gc_end: dev = (254,48), ret = -61, seg_freed = 0, sec_freed = 0, nodes = 1562, dents = 2, imeta = 18, free_sec:44898, free_seg:44898, rsv_seg:239, prefree_seg:0
>
> Fixes: d98af5f45520 ("f2fs: introduce gc_urgent_mid mode")
> Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
> ---
>   fs/f2fs/gc.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index e40bdd1..daecf69 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -257,6 +257,7 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
>   
>   	switch (sbi->gc_mode) {
>   	case GC_IDLE_CB:
> +	case GC_URGENT_MID:
>   		gc_mode = GC_CB;
>   		break;
>   	case GC_IDLE_GREEDY: