On 07/03, Chao Yu wrote:
> On 2023/6/15 0:10, Jaegeuk Kim wrote:
> > If there're huge # of small discards, this will increase checkpoint latency
> > insanely. Let's issue small discards only by trim.
> >
> > Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
> > ---
> >
> > Change log from v1:
> > - move the skip logic to avoid dangling objects
> >
> > fs/f2fs/segment.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 8c7af8b4fc47..0457d620011f 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -2193,7 +2193,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info
> > *sbi,
> > len = next_pos - cur_pos;
> > if (f2fs_sb_has_blkzoned(sbi) ||
> > - (force && len < cpc->trim_minlen))
> > + !force || len < cpc->trim_minlen)
> > goto skip;
>
> Sorry for late reply.
>
> We have a configuration for such case, what do you think of setting
> max_small_discards to zero? otherwise, w/ above change, max_small_discards
> logic may be broken?
>
> What: /sys/fs/f2fs/<disk>/max_small_discards
> Date: November 2013
> Contact: "Jaegeuk Kim" <jaegeuk....@samsung.com>
> Description: Controls the issue rate of discard commands that consist of
> small
> blocks less than 2MB. The candidates to be discarded are
> cached until
> checkpoint is triggered, and issued during the checkpoint.
> By default, it is disabled with 0.
>
> Or, if we prefer to disable small_discards by default, what about below
> change:
I think small_discards is fine, but need to avoid long checkpoint latency only.
>
> From eb89d9b56e817e3046d7fa17165b12416f09d456 Mon Sep 17 00:00:00 2001
> From: Chao Yu <c...@kernel.org>
> Date: Mon, 3 Jul 2023 09:06:53 +0800
> Subject: [PATCH] Revert "f2fs: enable small discard by default"
>
> This reverts commit d618ebaf0aa83d175658aea5291e0c459d471d39 in order
> to disable small discard by default, so that if there're huge number of
> small discards, it will decrease checkpoint's latency obviously.
>
> Also, this patch reverts 9ac00e7cef10 ("f2fs: do not issue small discard
> commands during checkpoint"), due to it breaks small discard feature which
> may be configured via sysfs entry max_small_discards.
>
> Fixes: 9ac00e7cef10 ("f2fs: do not issue small discard commands during
> checkpoint")
> Signed-off-by: Chao Yu <c...@kernel.org>
> ---
> fs/f2fs/segment.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 14c822e5c9c9..0a313368f18b 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2193,7 +2193,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info
> *sbi,
> len = next_pos - cur_pos;
>
> if (f2fs_sb_has_blkzoned(sbi) ||
> - !force || len < cpc->trim_minlen)
> + (force && len < cpc->trim_minlen))
> goto skip;
>
> f2fs_issue_discard(sbi, entry->start_blkaddr + cur_pos,
> @@ -2269,7 +2269,7 @@ static int create_discard_cmd_control(struct
> f2fs_sb_info *sbi)
> atomic_set(&dcc->queued_discard, 0);
> atomic_set(&dcc->discard_cmd_cnt, 0);
> dcc->nr_discards = 0;
> - dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
> + dcc->max_discards = 0;
> dcc->max_discard_request = DEF_MAX_DISCARD_REQUEST;
> dcc->min_discard_issue_time = DEF_MIN_DISCARD_ISSUE_TIME;
> dcc->mid_discard_issue_time = DEF_MID_DISCARD_ISSUE_TIME;
> --
> 2.40.1
>
>
>
> > f2fs_issue_discard(sbi, entry->start_blkaddr + cur_pos,
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