linux-kernel - Re: [PATCH V2] f2fs: fix to avoid use GC_AT when setting gc_mode as GC_URGENT_LOW or GC_URGENT

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Message-ID: <CAHJ8P3LrnCYo_ETa7XPty_keAmPd_z8V9A2Bp6gDaxBMCxpPSA@mail.gmail.com>
Date: Mon, 28 Oct 2024 18:29:05 +0800
From: Zhiguo Niu <niuzhiguo84@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: Zhiguo Niu <zhiguo.niu@...soc.com>, jaegeuk@...nel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, 
	ke.wang@...soc.com, Hao_hao.Wang@...soc.com
Subject: Re: [PATCH V2] f2fs: fix to avoid use GC_AT when setting gc_mode as
 GC_URGENT_LOW or GC_URGENT_MID

Chao Yu <chao@...nel.org> 于2024年10月28日周一 17:34写道：
>
> On 2024/10/23 11:08, Zhiguo Niu wrote:
> > 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.
>
> The code looks fine to me, there is one more thing, can you please update
> description of gc_urgent in sysfs-fs-f2fs? so it can describe explicitly
> that configuring gc_urgent to low or mid will setup GC_CB GC policy which
> will override GC_AT.
Dear Chao,
OK, thanks for you suggestions.

>
> 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: 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@...soc.com>
> > ---
> > 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:
>