linux-kernel - Re: [PATCH 1/2] f2fs: Optimize excessive write operations caused by continuous background garbage collection in Zoned UFS

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Message-ID: <aMjLMwNDjabD8MVH@google.com>
Date: Tue, 16 Sep 2025 02:28:03 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Liao Yuanhong <liaoyuanhong@...o.com>
Cc: Chao Yu <chao@...nel.org>,
	"open list:F2FS FILE SYSTEM" <linux-f2fs-devel@...ts.sourceforge.net>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] f2fs: Optimize excessive write operations caused by
 continuous background garbage collection in Zoned UFS

Could you please share some trends of relation between has_enough_free_blocks()
vs. has_enough_dirty_blocks()? I'm wondering whethere there's a missing case
where has_enough_free_blocks() is not enough.

On 09/09, Liao Yuanhong wrote:
> Incorporate a check using has_enough_dirty_blocks() to prevent redundant
> background GC in Zoned UFS. When there are insufficient dirty segments,
> continuous execution of background GC should be avoided, as it results in
> unnecessary write operations and impacts device lifespan. The initial
> threshold is set to 3 * section size (since f2fs data uses three write
> pointers).
> 
> Signed-off-by: Liao Yuanhong <liaoyuanhong@...o.com>
> ---
>  fs/f2fs/gc.c |  8 ++++++--
>  fs/f2fs/gc.h | 10 +++++++++-
>  2 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index ed3acbfc83ca..4a8c08f970e3 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -120,7 +120,9 @@ static int gc_thread_func(void *data)
>  
>  		if (f2fs_sb_has_blkzoned(sbi)) {
>  			if (has_enough_free_blocks(sbi,
> -				gc_th->no_zoned_gc_percent)) {
> +				gc_th->no_zoned_gc_percent) ||
> +				!has_enough_dirty_blocks(sbi,
> +				LIMIT_GC_DIRTY_SECTION_NUM)) {
>  				wait_ms = gc_th->no_gc_sleep_time;
>  				f2fs_up_write(&sbi->gc_lock);
>  				goto next;
> @@ -1750,7 +1752,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>  
>  			if (f2fs_sb_has_blkzoned(sbi) &&
>  					!has_enough_free_blocks(sbi,
> -					sbi->gc_thread->boost_zoned_gc_percent))
> +					sbi->gc_thread->boost_zoned_gc_percent) &&
> +					has_enough_dirty_blocks(sbi,
> +					LIMIT_GC_DIRTY_SECTION_NUM))
>  				window_granularity *=
>  					sbi->gc_thread->boost_gc_multiple;
>  
> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
> index 24e8b1c27acc..1ef234c2702b 100644
> --- a/fs/f2fs/gc.h
> +++ b/fs/f2fs/gc.h
> @@ -36,6 +36,7 @@
>  #define DEF_MIGRATION_WINDOW_GRANULARITY_ZONED	3
>  #define BOOST_GC_MULTIPLE	5
>  #define ZONED_PIN_SEC_REQUIRED_COUNT	1
> +#define LIMIT_GC_DIRTY_SECTION_NUM	3
>  
>  #define DEF_GC_FAILED_PINNED_FILES	2048
>  #define MAX_GC_FAILED_PINNED_FILES	USHRT_MAX
> @@ -177,6 +178,12 @@ static inline bool has_enough_free_blocks(struct f2fs_sb_info *sbi,
>  	return free_sections(sbi) > ((sbi->total_sections * limit_perc) / 100);
>  }
>  
> +static inline bool has_enough_dirty_blocks(struct f2fs_sb_info *sbi,
> +						unsigned int limit_num)
> +{
> +	return dirty_segments(sbi) > limit_num * SEGS_PER_SEC(sbi);
> +}
> +
>  static inline bool has_enough_invalid_blocks(struct f2fs_sb_info *sbi)
>  {
>  	block_t user_block_count = sbi->user_block_count;
> @@ -197,6 +204,7 @@ static inline bool need_to_boost_gc(struct f2fs_sb_info *sbi)
>  {
>  	if (f2fs_sb_has_blkzoned(sbi))
>  		return !has_enough_free_blocks(sbi,
> -				sbi->gc_thread->boost_zoned_gc_percent);
> +				sbi->gc_thread->boost_zoned_gc_percent) &&
> +				has_enough_dirty_blocks(sbi, LIMIT_GC_DIRTY_SECTION_NUM);
>  	return has_enough_invalid_blocks(sbi);
>  }
> -- 
> 2.34.1