linux-kernel - Re: [f2fs-dev] [PATCH 1/3] f2fs: use f2fs_submit_page_bio for ra_meta

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Date:   Wed, 10 May 2017 19:41:23 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/3] f2fs: use f2fs_submit_page_bio for
 ra_meta_pages

On 05/11, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2017/5/11 7:48, Jaegeuk Kim wrote:
> > This patch avoids to use f2fs_submit_merged_bio for read, which was the only
> > read case.
> 
> This makes f2fs losing the chance to merge multiple pages into one bio during
> reading continuous physical blocks, it may cause potential performance
> regression, how about using a local bio in ra_meta_pages to cache more pages?

This is a readahead flow, which is asynchronous and not a performance critical
flow. And, I expect blk_plug is still able to merge them. We're using this in
readahead of node blocks as well.

Thanks,

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >  fs/f2fs/checkpoint.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index ea9c317b5916..8d92f8249000 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -207,12 +207,10 @@ int ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
> >  		}
> >  
> >  		fio.page = page;
> > -		fio.old_blkaddr = fio.new_blkaddr;
> > -		f2fs_submit_page_mbio(&fio);
> > +		f2fs_submit_page_bio(&fio);
> >  		f2fs_put_page(page, 0);
> >  	}
> >  out:
> > -	f2fs_submit_merged_bio(sbi, META, READ);
> >  	blk_finish_plug(&plug);
> >  	return blkno - start;
> >  }
> >