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

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Date:   Tue, 11 May 2021 09:30:21 +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 2021/5/10 22:47, Jaegeuk Kim wrote:
> On 05/06, Chao Yu wrote:
>> 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?
> 
> I just gave an example. And default is default.
> 
>>
>>> 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?
> 
> I think both, and we set it as hot.

Then hot and cold bit will set to the same db file after defragmentation?

Thanks,

> 
>>
>> 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;
>>>>>
>>> .
>>>
> .
>