Re: [f2fs-dev] [PATCH 2/2] f2fs: read contiguous sit entry pagesby merging for mount performance

[Gu Zheng]

Hi Yu,
On 11/12/2013 01:18 PM, Chao Yu wrote:

> Previously we read sit entries page one by one, this method lost the chance of reading contiguous page together.
> So we read pages as contiguous as possible for better mount performance.
> 
> Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
> ---
>  fs/f2fs/f2fs.h    |    2 ++
>  fs/f2fs/segment.c |   65 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>  fs/f2fs/segment.h |    2 ++
>  3 files changed, 66 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 0afdcec..bfe9d87 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1113,6 +1113,8 @@ struct page *find_data_page(struct inode *, pgoff_t, bool);
>  struct page *get_lock_data_page(struct inode *, pgoff_t);
>  struct page *get_new_data_page(struct inode *, struct page *, pgoff_t, bool);
>  int f2fs_readpage(struct f2fs_sb_info *, struct page *, block_t, int);
> +void f2fs_submit_read_bio(struct f2fs_sb_info *, int);
> +void submit_read_page(struct f2fs_sb_info *, struct page *, block_t, int);

Better to move these declarations into PATCH 1/2.

>  int do_write_data_page(struct page *);
>  
>  /*
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 86dc289..414c351 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1474,19 +1474,72 @@ static int build_curseg(struct f2fs_sb_info *sbi)
>  	return restore_curseg_summaries(sbi);
>  }
>  
> +static int ra_sit_pages(struct f2fs_sb_info *sbi, int start,
> +					int nrpages, bool *is_order)
> +{
> +	struct address_space *mapping = sbi->meta_inode->i_mapping;
> +	struct sit_info *sit_i = SIT_I(sbi);
> +	struct page *page;
> +	block_t blk_addr;
> +	int blkno, readcnt = 0;
> +	int sit_blk_cnt = SIT_BLK_CNT(sbi);
> +
> +	for (blkno = start; blkno < start + nrpages; blkno++) {
> +
> +		if (blkno >= sit_blk_cnt)

Merge these two judgements:
for (blkno = start; blkno < start + nrpages && blkno < sit_blk_cnt; blkno++)

> +			goto out;

> +		if ((!f2fs_test_bit(blkno, sit_i->sit_bitmap) ^ !*is_order)) {
> +			*is_order = !*is_order;
> +			goto out;

'Break' seems more suitable.

> +		}
> +
> +		blk_addr = sit_i->sit_base_addr + blkno;
> +		if (*is_order)
> +			blk_addr += sit_i->sit_blocks;
> +repeat:
> +		page = grab_cache_page(mapping, blk_addr);
> +		if (!page) {
> +			cond_resched();
> +			goto repeat;
> +		}
> +		if (PageUptodate(page)) {
> +			f2fs_put_page(page, 1);
> +			readcnt++;
> +			goto out;

Here may be 'Continue'.

> +		}
> +
> +		submit_read_page(sbi, page, blk_addr, READ_SYNC);
> +
> +		page_cache_release(page);

Put page here seems not a good idea, otherwise all your work may be in vain.

> +		readcnt++;
> +	}
> +out:
> +	f2fs_submit_read_bio(sbi, READ_SYNC);
> +	return readcnt;
> +}
> +
>  static void build_sit_entries(struct f2fs_sb_info *sbi)
>  {
>  	struct sit_info *sit_i = SIT_I(sbi);
>  	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_COLD_DATA);
>  	struct f2fs_summary_block *sum = curseg->sum_blk;
> -	unsigned int start;
> +	bool is_order = f2fs_test_bit(0, sit_i->sit_bitmap) ? true : false;
> +	int sit_blk_cnt = SIT_BLK_CNT(sbi);
> +	int bio_blocks = MAX_BIO_BLOCKS(max_hw_blocks(sbi));
> +	unsigned int i, start, end;
> +	unsigned int readed, start_blk = 0;
>  
> -	for (start = 0; start < TOTAL_SEGS(sbi); start++) {
> +next:
> +	readed = ra_sit_pages(sbi, start_blk, bio_blocks, &is_order);

In fact, you know how many blocks that you want to read(SIT_BLK_CNT(sbi)),
so here sit_blk_cnt is more suitable than a MAX one, and it also can make
the logic of ra_sit_pages more simple.

> +
> +	start = start_blk * sit_i->sents_per_block;
> +	end = (start_blk + readed) * sit_i->sents_per_block;
> +
> +	for (; start < end && start < TOTAL_SEGS(sbi); start++) {
>  		struct seg_entry *se = &sit_i->sentries[start];
>  		struct f2fs_sit_block *sit_blk;
>  		struct f2fs_sit_entry sit;
>  		struct page *page;
> -		int i;
>  
>  		mutex_lock(&curseg->curseg_mutex);
>  		for (i = 0; i < sits_in_cursum(sum); i++) {
> @@ -1497,6 +1550,7 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
>  			}
>  		}
>  		mutex_unlock(&curseg->curseg_mutex);
> +
>  		page = get_current_sit_page(sbi, start);
>  		sit_blk = (struct f2fs_sit_block *)page_address(page);
>  		sit = sit_blk->entries[SIT_ENTRY_OFFSET(sit_i, start)];
> @@ -1509,6 +1563,11 @@ got_it:
>  			e->valid_blocks += se->valid_blocks;
>  		}
>  	}
> +
> +	start_blk += readed;
> +	if (start_blk >= sit_blk_cnt)
> +		return;
> +	goto next;

Using do {...} while(start_blk < sit_blk_cnt) rather than the so big upstream goto.

>  }
>  
>  static void init_free_segmap(struct f2fs_sb_info *sbi)
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 269f690..ad5b9f1 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -83,6 +83,8 @@
>  	(segno / SIT_ENTRY_PER_BLOCK)
>  #define	START_SEGNO(sit_i, segno)		\
>  	(SIT_BLOCK_OFFSET(sit_i, segno) * SIT_ENTRY_PER_BLOCK)
> +#define SIT_BLK_CNT(sbi)			\
> +	((TOTAL_SEGS(sbi) + SIT_ENTRY_PER_BLOCK - 1) / SIT_ENTRY_PER_BLOCK)
>  #define f2fs_bitmap_size(nr)			\
>  	(BITS_TO_LONGS(nr) * sizeof(unsigned long))
>  #define TOTAL_SEGS(sbi)	(SM_I(sbi)->main_segments)


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