On 2016/10/19 2:48, Jaegeuk Kim wrote:
> We don't need to allocate bio partially in order to maximize sequential 
> writes.

We are going to allocate bio with max size supposing that there will be more
opportunity to merge small IOs into one bio. Otherwise, if MAX_BIO_BLOCKS is
smaller than BIO_MAX_PAGES, less IOs can be merged. Is my understanding correct?

Thanks,

> 
> Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
> ---
>  fs/f2fs/checkpoint.c |  2 +-
>  fs/f2fs/data.c       |  4 +---
>  fs/f2fs/node.c       |  3 +--
>  fs/f2fs/segment.c    |  4 ++--
>  fs/f2fs/segment.h    | 17 +++--------------
>  5 files changed, 8 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 654f5d7..157b7fd 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -228,7 +228,7 @@ void ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t 
> index)
>       f2fs_put_page(page, 0);
>  
>       if (readahead)
> -             ra_meta_pages(sbi, index, MAX_BIO_BLOCKS(sbi), META_POR, true);
> +             ra_meta_pages(sbi, index, BIO_MAX_PAGES, META_POR, true);
>  }
>  
>  static int f2fs_write_meta_page(struct page *page,
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 77cd9ac..fe8ce5a 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -307,10 +307,8 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
>               __submit_merged_bio(io);
>  alloc_new:
>       if (io->bio == NULL) {
> -             int bio_blocks = MAX_BIO_BLOCKS(sbi);
> -
>               io->bio = __bio_alloc(sbi, fio->new_blkaddr,
> -                                             bio_blocks, is_read);
> +                                             BIO_MAX_PAGES, is_read);
>               io->fio = *fio;
>       }
>  
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 69c42e2..285e2a5 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -2101,7 +2101,6 @@ int restore_node_summary(struct f2fs_sb_info *sbi,
>       struct f2fs_node *rn;
>       struct f2fs_summary *sum_entry;
>       block_t addr;
> -     int bio_blocks = MAX_BIO_BLOCKS(sbi);
>       int i, idx, last_offset, nrpages;
>  
>       /* scan the node segment */
> @@ -2110,7 +2109,7 @@ int restore_node_summary(struct f2fs_sb_info *sbi,
>       sum_entry = &sum->entries[0];
>  
>       for (i = 0; i < last_offset; i += nrpages, addr += nrpages) {
> -             nrpages = min(last_offset - i, bio_blocks);
> +             nrpages = min(last_offset - i, BIO_MAX_PAGES);
>  
>               /* readahead node pages */
>               ra_meta_pages(sbi, addr, nrpages, META_POR, true);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 7a7e3f1..a21a1a3 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2355,10 +2355,10 @@ static void build_sit_entries(struct f2fs_sb_info 
> *sbi)
>       int sit_blk_cnt = SIT_BLK_CNT(sbi);
>       unsigned int i, start, end;
>       unsigned int readed, start_blk = 0;
> -     int nrpages = MAX_BIO_BLOCKS(sbi) * 8;
>  
>       do {
> -             readed = ra_meta_pages(sbi, start_blk, nrpages, META_SIT, true);
> +             readed = ra_meta_pages(sbi, start_blk, BIO_MAX_PAGES,
> +                                                     META_SIT, true);
>  
>               start = start_blk * sit_i->sents_per_block;
>               end = (start_blk + readed) * sit_i->sents_per_block;
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index a6efb5c..d8ff069 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -102,8 +102,6 @@
>       (((sector_t)blk_addr) << F2FS_LOG_SECTORS_PER_BLOCK)
>  #define SECTOR_TO_BLOCK(sectors)                                     \
>       (sectors >> F2FS_LOG_SECTORS_PER_BLOCK)
> -#define MAX_BIO_BLOCKS(sbi)                                          \
> -     ((int)min((int)max_hw_blocks(sbi), BIO_MAX_PAGES))
>  
>  /*
>   * indicate a block allocation direction: RIGHT and LEFT.
> @@ -698,13 +696,6 @@ static inline bool sec_usage_check(struct f2fs_sb_info 
> *sbi, unsigned int secno)
>       return false;
>  }
>  
> -static inline unsigned int max_hw_blocks(struct f2fs_sb_info *sbi)
> -{
> -     struct block_device *bdev = sbi->sb->s_bdev;
> -     struct request_queue *q = bdev_get_queue(bdev);
> -     return SECTOR_TO_BLOCK(queue_max_sectors(q));
> -}
> -
>  /*
>   * It is very important to gather dirty pages and write at once, so that we 
> can
>   * submit a big bio without interfering other data writes.
> @@ -722,7 +713,7 @@ static inline int nr_pages_to_skip(struct f2fs_sb_info 
> *sbi, int type)
>       else if (type == NODE)
>               return 8 * sbi->blocks_per_seg;
>       else if (type == META)
> -             return 8 * MAX_BIO_BLOCKS(sbi);
> +             return 8 * BIO_MAX_PAGES;
>       else
>               return 0;
>  }
> @@ -739,11 +730,9 @@ static inline long nr_pages_to_write(struct f2fs_sb_info 
> *sbi, int type,
>               return 0;
>  
>       nr_to_write = wbc->nr_to_write;
> -
> +     desired = BIO_MAX_PAGES;
>       if (type == NODE)
> -             desired = 2 * max_hw_blocks(sbi);
> -     else
> -             desired = MAX_BIO_BLOCKS(sbi);
> +             desired <<= 1;
>  
>       wbc->nr_to_write = desired;
>       return desired - nr_to_write;
> 


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