linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: merge read IOs at ra_nat

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Date:	Fri, 22 Nov 2013 12:41:19 +0900
From:	Changman Lee <cm224.lee@...sung.com>
To:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: merge read IOs at ra_nat_pages()


How about doing mark_page_accessed(page) in ra_nat_pages like
ra_sit_pages to prevent readahead pages are reclaimed by VM?

On 목, 2013-11-21 at 18:35 +0900, Jaegeuk Kim wrote:
> This patch changes the policy of submitting read bios at ra_nat_pages.
> 
> Previously, f2fs submits small read bios with block plugging.
> But, with this patch, f2fs itself merges read bios first and then submits a
> large bio, which can reduce the bio handling overheads.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> ---
>  fs/f2fs/node.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index b843a5b..c06871f 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -89,13 +89,10 @@ static void ra_nat_pages(struct f2fs_sb_info *sbi, int nid)
>  {
>  	struct address_space *mapping = sbi->meta_inode->i_mapping;
>  	struct f2fs_nm_info *nm_i = NM_I(sbi);
> -	struct blk_plug plug;
>  	struct page *page;
>  	pgoff_t index;
>  	int i;
>  
> -	blk_start_plug(&plug);
> -
>  	for (i = 0; i < FREE_NID_PAGES; i++, nid += NAT_ENTRY_PER_BLOCK) {
>  		if (nid >= nm_i->max_nid)
>  			nid = 0;
> @@ -108,12 +105,11 @@ static void ra_nat_pages(struct f2fs_sb_info *sbi, int nid)

mark_page_accessed(page);

>  			f2fs_put_page(page, 1);
>  			continue;
>  		}
> -		if (f2fs_readpage(sbi, page, index, READ))
> -			continue;
> +		submit_read_page(sbi, page, index, READ_SYNC);
>  

mark_page_accessed(page);

>  		f2fs_put_page(page, 0);
>  	}
> -	blk_finish_plug(&plug);
> +	f2fs_submit_read_bio(sbi, READ_SYNC);
>  }
>  
>  static struct nat_entry *__lookup_nat_cache(struct f2fs_nm_info *nm_i, nid_t n)


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