Re: [PATCH V2] f2fs: fix to avoid use GC_AT when setting gc_mode as GC_URGENT_LOW or GC_URGENT_MID

[Zhiguo Niu]

Dear Chao,
any suggestions about this patch version? base your kindly suggestions
on patch v1
this is the issue encountered when I test GC.
thanks!

Zhiguo Niu <zhiguo.niu@xxxxxxxxxx> 于2024年10月23日周三 11:08写道：
>
> If gc_mode is set to GC_URGENT_LOW or GC_URGENT_MID, cost benefit GC
> approach should be used, 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.
>
> 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: 0e5e81114de1 ("f2fs: add GC_URGENT_LOW mode in gc_urgent")
> Fixes: d98af5f45520 ("f2fs: introduce gc_urgent_mid mode")
> Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
> ---
> v2: make GC_URGENT_LOW also use CB approach
> ---
>  fs/f2fs/gc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index e40bdd1..3e1b6d2 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -257,6 +257,8 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
>
>         switch (sbi->gc_mode) {
>         case GC_IDLE_CB:
> +       case GC_URGENT_LOW:
> +       case GC_URGENT_MID:
>                 gc_mode = GC_CB;
>                 break;
>         case GC_IDLE_GREEDY:
> --
> 1.9.1
>