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Message-ID: <81348540-e3aa-4907-94cd-df0c408e66e0@kernel.org>
Date: Thu, 8 May 2025 17:38:48 +0800
From: Chao Yu <chao@...nel.org>
To: "yohan.joung" <yohan.joung@...com>, jaegeuk@...nel.org,
daehojeong@...gle.com
Cc: chao@...nel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, pilhyun.kim@...com
Subject: Re: [PATCH v4 2/2] f2fs: add ckpt_valid_blocks to the section entry
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@...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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