Re: [f2fs-dev] [PATCH] f2fs: separate IPU policy for fdatasync from F2FS_IPU_FSYNC

[Chao Yu <chao@kernel.org>]

On 2022/11/9 20:56, qixiaoyu wrote:
> On Tue, Nov 08, 2022 at 10:30:13PM +0800, Chao Yu wrote:
>> On 2022/11/8 20:32, qixiaoyu wrote:
>>> On Sun, Nov 06, 2022 at 09:54:59PM +0800, Chao Yu wrote:
>>>> On 2022/11/2 20:25, qixiaoyu wrote:
>>>>> Hi Chao,
>>>>>
>>>>> fdatasync do in-place-update to avoid additional node writes, but currently
>>>>> it only do that with F2FS_IPU_FSYNC as:
>>>>>
>>>>> f2fs_do_sync_file:
>>>>> 	if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
>>>>>   		set_inode_flag(inode, FI_NEED_IPU);
>>>>>
>>>>> check_inplace_update_policy:
>>>>> 	/* this is only set during fdatasync */
>>>>> 	if (policy & (0x1 << F2FS_IPU_FSYNC) &&
>>>>> 			is_inode_flag_set(inode, FI_NEED_IPU))
>>>>> 		return true;
>>>>>
>>>>> So this patch separate in-place-update of fdatasync from F2FS_IPU_FSYNC to
>>>>> apply it to all IPU policy.
>>>>>
>>>>> BTW, we found small performance improvement with this patch on AndroBench app
>>>>> using F2FS_IPU_SSR_UTIL on our product:
>>>>
>>>> How this patch affects performance when F2FS_IPU_SSR_UTIL is on?
>>>>
>>>> Thanks,
>>>>
>>>
>>> SQLite test in AndroBench app use fdatasync to sync file to the disk.
>>> When switch to F2FS_IPU_SSR_UTIL ipu_policy, it will use out-of-place-update
>>> even though SQLite calls fdatasync, which will introduce extra meta data write.
>>
>> Why not using F2FS_IPU_SSR_UTIL | F2FS_IPU_FSYNC, I guess these two flags
>> cover different scenarios, F2FS_IPU_SSR_UTIL for ssr case, and F2FS_IPU_FSYNC
>> for f{data,}sync case.
>>
>> Thanks,
>>
> 
> As fsync(2) says:
> fdatasync() is similar to fsync(), but does not flush modified metadata unless that
> metadata is needed in order to allow a subsequent data retrieval to be correctly handled.

I guess it says it allows fdatasync to flush metatdata in order to recovery data in SPO
case.

> 
> I think fdatasync should try to perform in-place-update to avoid unnecessary metadata
> update whatever the ipu_policy is, and F2FS_IPU_FSYNC is used for fsync independently.

IMO, FSYNC key word in F2FS_IPU_FSYNC means fsync path or interface name as below:

int (*fsync) (struct file *, loff_t, loff_t, int datasync);

And by default, f2fs enables F2FS_IPU_FSYNC, I didn't get why we need to disable it.

To Jaegeuk, any comments?

Thanks,

> 
> Thanks
> 
>>>
>>> Thanks.
>>>
>>>>>
>>>>>                  F2FS_IPU_FSYNC  F2FS_IPU_SSR_UTIL   F2FS_IPU_SSR_UTIL(with patch)
>>>>> SQLite Insert(QPS)  6818.08     6327.09(-7.20%)     6757.72
>>>>> SQLite Update(QPS)  6528.81     6336.57(-2.94%)     6490.77
>>>>> SQLite Delete(QPS)  9724.68     9378.37(-3.56%)     9622.27
>>>>>
>>>>> Thanks
>>>>>
>>>>> On Tue, Nov 01, 2022 at 11:14:55PM +0800, Chao Yu wrote:
>>>>>> On 2022/10/21 10:31, qixiaoyu1 wrote:
>>>>>>> Currently IPU policy for fdatasync is coupled with F2FS_IPU_FSYNC.
>>>>>>> Fix to apply it to all IPU policy.
>>>>>>
>>>>>> Xiaoyu,
>>>>>>
>>>>>> Sorry for the delay.
>>>>>>
>>>>>> I didn't get the point, can you please explain more about the
>>>>>> issue?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>>
>>>>>>> Signed-off-by: qixiaoyu1 <qixiaoyu1@xiaomi.com>
>>>>>>> ---
>>>>>>>   fs/f2fs/data.c | 8 +++-----
>>>>>>>   fs/f2fs/file.c | 4 +++-
>>>>>>>   2 files changed, 6 insertions(+), 6 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>>>> index a71e818cd67b..fec8e15fe820 100644
>>>>>>> --- a/fs/f2fs/data.c
>>>>>>> +++ b/fs/f2fs/data.c
>>>>>>> @@ -2518,6 +2518,9 @@ static inline bool check_inplace_update_policy(struct inode *inode,
>>>>>>>   	if (policy & (0x1 << F2FS_IPU_HONOR_OPU_WRITE) &&
>>>>>>>   			is_inode_flag_set(inode, FI_OPU_WRITE))
>>>>>>>   		return false;
>>>>>>> +	/* this is set by fdatasync or F2FS_IPU_FSYNC policy */
>>>>>>> +	if (is_inode_flag_set(inode, FI_NEED_IPU))
>>>>>>> +		return true;
>>>>>>>   	if (policy & (0x1 << F2FS_IPU_FORCE))
>>>>>>>   		return true;
>>>>>>>   	if (policy & (0x1 << F2FS_IPU_SSR) && f2fs_need_SSR(sbi))
>>>>>>> @@ -2538,11 +2541,6 @@ static inline bool check_inplace_update_policy(struct inode *inode,
>>>>>>>   			!IS_ENCRYPTED(inode))
>>>>>>>   		return true;
>>>>>>> -	/* this is only set during fdatasync */
>>>>>>> -	if (policy & (0x1 << F2FS_IPU_FSYNC) &&
>>>>>>> -			is_inode_flag_set(inode, FI_NEED_IPU))
>>>>>>> -		return true;
>>>>>>> -
>>>>>>>   	if (unlikely(fio && is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
>>>>>>>   			!f2fs_is_checkpointed_data(sbi, fio->old_blkaddr)))
>>>>>>>   		return true;
>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>>> index 82cda1258227..08091550cdf2 100644
>>>>>>> --- a/fs/f2fs/file.c
>>>>>>> +++ b/fs/f2fs/file.c
>>>>>>> @@ -270,8 +270,10 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>>>>>>>   		goto go_write;
>>>>>>>   	/* if fdatasync is triggered, let's do in-place-update */
>>>>>>> -	if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
>>>>>>> +	if (datasync || (SM_I(sbi)->ipu_policy & (0x1 << F2FS_IPU_FSYNC) &&
>>>>>>> +			get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks))
>>>>>>>   		set_inode_flag(inode, FI_NEED_IPU);
>>>>>>> +
>>>>>>>   	ret = file_write_and_wait_range(file, start, end);
>>>>>>>   	clear_inode_flag(inode, FI_NEED_IPU);


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