linux-kernel - Re: [PATCH] f2fs: set file as cold when file defragmentation

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Date:   Thu, 6 May 2021 14:36:12 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <daejun7.park@...sung.com>, "chao@...nel.org" <chao@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [PATCH] f2fs: set file as cold when file defragmentation

On 2021/5/6 12:46, Jaegeuk Kim wrote:
> On 05/06, Chao Yu wrote:
>> On 2021/4/29 14:20, Daejun Park wrote:
>>> In file defragmentation by ioctl, all data blocks in the file are
>>> re-written out-of-place. File defragmentation implies user will not update
>>> and mostly read the file. So before the defragmentation, we set file
>>> temperature as cold for better block allocation.
>>
>> I don't think all fragmented files are cold, e.g. db file.
> 
> I have a bit different opinion. I think one example would be users want to
> defragment a file, when the they want to get higher read bandwidth for

Multimedia file was already defined as cold file now via default extension
list?

> usually multimedia files. That's likely to be cold files. Moreover, I don't
> think they want to defragment db files which will be fragmented soon?

I guess like db files have less update but more access?

Thanks,

> 
>>
>> We have separated interface (via f2fs_xattr_advise_handler, e.g. setfattr -n
>> "system.advise" -v value) to indicate this file is a hot/cold file, so my
>> suggestion is after file defragmentation, if you think this file is cold, and
>> use setxattr() to set it as cold.
>>
>> Thanks,
>>
>>>
>>> Signed-off-by: Daejun Park <daejun7.park@...sung.com>
>>> ---
>>>    fs/f2fs/file.c | 3 +++
>>>    1 file changed, 3 insertions(+)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index d697c8900fa7..dcac965a05fe 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -2669,6 +2669,9 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
>>>    	map.m_len = pg_end - pg_start;
>>>    	total = 0;
>>> +	if (!file_is_cold(inode))
>>> +		file_set_cold(inode);
>>> +
>>>    	while (map.m_lblk < pg_end) {
>>>    		pgoff_t idx;
>>>    		int cnt = 0;
>>>
> .
>