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

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Date:   Thu, 11 May 2017 11:22:23 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
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 2017/5/11 10:41, Jaegeuk Kim wrote:
> 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.

Confirmed, block plug can do the merge. :)

Thanks,

> 
> 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;
>>>  }
>>>
> 
> .
>