Re: [f2fs-dev] [PATCH v4 2/2] f2fs: add ckpt_valid_blocks to the section entry

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 5/8/25 15:47, yohan.joung wrote:
> when performing buffered writes in a large section,
> overhead is incurred due to the iteration through
> ckpt_valid_blocks within the section.
> when SEGS_PER_SEC is 128, this overhead accounts for 20% within
> the f2fs_write_single_data_page routine.
> as the size of the section increases, the overhead also grows.
> to handle this problem ckpt_valid_blocks is
> added within the section entries.
> 
> Test
> insmod null_blk.ko nr_devices=1 completion_nsec=1  submit_queues=8
> hw_queue_depth=64 max_sectors=512 bs=4096 memory_backed=1
> make_f2fs /dev/block/nullb0
> make_f2fs -s 128 /dev/block/nullb0
> fio --bs=512k --size=1536M --rw=write --name=1
> --filename=/mnt/test_dir/seq_write
> --ioengine=io_uring --iodepth=64 --end_fsync=1
> 
> before
> SEGS_PER_SEC 1
> 2556MiB/s
> SEGS_PER_SEC 128
> 2145MiB/s
> 
> after
> SEGS_PER_SEC 1
> 2556MiB/s
> SEGS_PER_SEC 128
> 2556MiB/s
> 
> Signed-off-by: yohan.joung <yohan.joung@sk.com>
> ---
>  fs/f2fs/segment.c | 41 +++++++++++++++++++++++++++++-------
>  fs/f2fs/segment.h | 53 +++++++++++++++++++++++++++++++++++++----------
>  2 files changed, 76 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 671bc5a8fd4a..7a53f2d8a474 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2447,7 +2447,7 @@ static void update_segment_mtime(struct f2fs_sb_info *sbi, block_t blkaddr,
>   * that the consecutive input blocks belong to the same segment.
>   */
>  static int update_sit_entry_for_release(struct f2fs_sb_info *sbi, struct seg_entry *se,
> -				block_t blkaddr, unsigned int offset, int del)
> +				unsigned int segno, block_t blkaddr, unsigned int offset, int del)
>  {
>  	bool exist;
>  #ifdef CONFIG_F2FS_CHECK_FS
> @@ -2492,15 +2492,22 @@ static int update_sit_entry_for_release(struct f2fs_sb_info *sbi, struct seg_ent
>  				f2fs_test_and_clear_bit(offset + i, se->discard_map))
>  			sbi->discard_blks++;
>  
> -		if (!f2fs_test_bit(offset + i, se->ckpt_valid_map))
> +#ifdef CONFIG_F2FS_CHECK_FS
> +		if (__is_large_section(sbi))
> +			sanity_check_valid_blocks(sbi, segno);
> +#endif
> +		if (!f2fs_test_bit(offset + i, se->ckpt_valid_map)) {
>  			se->ckpt_valid_blocks -= 1;
> +			if (__is_large_section(sbi))
> +				get_sec_entry(sbi, segno)->ckpt_valid_blocks -= 1;
> +		}
>  	}
>  
>  	return del;
>  }
>  
>  static int update_sit_entry_for_alloc(struct f2fs_sb_info *sbi, struct seg_entry *se,
> -				block_t blkaddr, unsigned int offset, int del)
> +				unsigned int segno, block_t blkaddr, unsigned int offset, int del)
>  {
>  	bool exist;
>  #ifdef CONFIG_F2FS_CHECK_FS
> @@ -2532,13 +2539,23 @@ static int update_sit_entry_for_alloc(struct f2fs_sb_info *sbi, struct seg_entry
>  	 * SSR should never reuse block which is checkpointed
>  	 * or newly invalidated.
>  	 */
> +#ifdef CONFIG_F2FS_CHECK_FS
> +	if (__is_large_section(sbi))
> +		sanity_check_valid_blocks(sbi, segno);
> +#endif

How about doing sanity check after ckpt_valid_blocks update?

>  	if (!is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
> -		if (!f2fs_test_and_set_bit(offset, se->ckpt_valid_map))
> +		if (!f2fs_test_and_set_bit(offset, se->ckpt_valid_map)) {
>  			se->ckpt_valid_blocks++;
> +			if (__is_large_section(sbi))
> +				get_sec_entry(sbi, segno)->ckpt_valid_blocks++;
> +		}
>  	}
>  
> -	if (!f2fs_test_bit(offset, se->ckpt_valid_map))
> +	if (!f2fs_test_bit(offset, se->ckpt_valid_map)) {
>  		se->ckpt_valid_blocks += del;
> +		if (__is_large_section(sbi))
> +			get_sec_entry(sbi, segno)->ckpt_valid_blocks += del;
> +	}
>  
>  	return del;
>  }
> @@ -2569,9 +2586,9 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
>  
>  	/* Update valid block bitmap */
>  	if (del > 0) {
> -		del = update_sit_entry_for_alloc(sbi, se, blkaddr, offset, del);
> +		del = update_sit_entry_for_alloc(sbi, se, segno, blkaddr, offset, del);
>  	} else {
> -		del = update_sit_entry_for_release(sbi, se, blkaddr, offset, del);
> +		del = update_sit_entry_for_release(sbi, se, segno, blkaddr, offset, del);
>  	}
>  
>  	__mark_sit_entry_dirty(sbi, segno);
> @@ -4700,12 +4717,16 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  					&sit_in_journal(journal, offset));
>  				check_block_count(sbi, segno,
>  					&sit_in_journal(journal, offset));
> +				if (__is_large_section(sbi))
> +					set_ckpt_valid_blocks(sbi, segno);
>  			} else {
>  				sit_offset = SIT_ENTRY_OFFSET(sit_i, segno);
>  				seg_info_to_raw_sit(se,
>  						&raw_sit->entries[sit_offset]);
>  				check_block_count(sbi, segno,
>  						&raw_sit->entries[sit_offset]);
> +				if (__is_large_section(sbi))
> +					set_ckpt_valid_blocks(sbi, segno);
>  			}

Move here for cleanup?

if (__is_large_section(sbi))
	set_ckpt_valid_blocks(sbi, segno);

How about adding sanity check here as well?

>  
>  			__clear_bit(segno, bitmap);
> @@ -5029,6 +5050,12 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>  	}
>  	up_read(&curseg->journal_rwsem);
>  
> +	/* update ckpt_ckpt_valid_block */
> +	if (__is_large_section(sbi)) {
> +		for (unsigned int segno = 0; segno < MAIN_SEGS(sbi); segno += SEGS_PER_SEC(sbi))

Let's keep the style of defining variable outside of 'for' statement.

> +			set_ckpt_valid_blocks(sbi, segno);
> +	}

do sanity check here?

> +
>  	if (err)
>  		return err;
>  
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 5777b385e7d2..ebc90d3cb57c 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -211,6 +211,7 @@ struct seg_entry {
>  
>  struct sec_entry {
>  	unsigned int valid_blocks;	/* # of valid blocks in a section */
> +	unsigned int ckpt_valid_blocks; /* # of valid blocks last cp in a section */
>  };
>  
>  #define MAX_SKIP_GC_COUNT			16
> @@ -347,22 +348,52 @@ static inline unsigned int get_valid_blocks(struct f2fs_sb_info *sbi,
>  static inline unsigned int get_ckpt_valid_blocks(struct f2fs_sb_info *sbi,
>  				unsigned int segno, bool use_section)
>  {
> -	if (use_section && __is_large_section(sbi)) {
> -		unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> -		unsigned int start_segno = GET_SEG_FROM_SEC(sbi, secno);
> -		unsigned int blocks = 0;
> -		int i;
> +	if (use_section && __is_large_section(sbi))
> +		return get_sec_entry(sbi, segno)->ckpt_valid_blocks;
> +	else
> +		return get_seg_entry(sbi, segno)->ckpt_valid_blocks;
> +}
> +
> +static inline void set_ckpt_valid_blocks(struct f2fs_sb_info *sbi,
> +		unsigned int segno)
> +{
> +	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> +	unsigned int start_segno = GET_SEG_FROM_SEC(sbi, secno);
> +	unsigned int blocks = 0;
> +	int i;
>  
> -		for (i = 0; i < SEGS_PER_SEC(sbi); i++, start_segno++) {
> -			struct seg_entry *se = get_seg_entry(sbi, start_segno);
> +	for (i = 0; i < SEGS_PER_SEC(sbi); i++, start_segno++) {
> +		struct seg_entry *se = get_seg_entry(sbi, start_segno);
>  
> -			blocks += se->ckpt_valid_blocks;
> -		}
> -		return blocks;
> +		blocks += se->ckpt_valid_blocks;
>  	}
> -	return get_seg_entry(sbi, segno)->ckpt_valid_blocks;
> +	get_sec_entry(sbi, segno)->ckpt_valid_blocks = blocks;
>  }
>  
> +#ifdef CONFIG_F2FS_CHECK_FS
> +static inline void sanity_check_valid_blocks(struct f2fs_sb_info *sbi,
> +		unsigned int segno)
> +{
> +	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> +	unsigned int start_segno = GET_SEG_FROM_SEC(sbi, secno);
> +	unsigned int blocks = 0;
> +	int i;
> +
> +	for (i = 0; i < SEGS_PER_SEC(sbi); i++, start_segno++) {
> +		struct seg_entry *se = get_seg_entry(sbi, start_segno);
> +
> +		blocks += se->ckpt_valid_blocks;
> +	}
> +
> +	if (blocks != get_sec_entry(sbi, segno)->ckpt_valid_blocks) {
> +		f2fs_err(sbi,
> +			"Inconsistent ckpt valid blocks: "
> +			"seg entry(%d) vs sec entry(%d) at secno %d",
> +			blocks, get_sec_entry(sbi, segno)->ckpt_valid_blocks, secno);
> +		f2fs_bug_on(sbi, 1);
> +	}
> +}
> +#endif

#else
static inline void sanity_check_valid_blocks(struct f2fs_sb_info *sbi,
			unsigned int segno)
{
}
#endif

Then we don't need to cover sanity_check_valid_blocks() invoking w/
CONFIG_F2FS_CHECK_FS.

Thanks,

>  static inline void seg_info_from_raw_sit(struct seg_entry *se,
>  					struct f2fs_sit_entry *rs)
>  {



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