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

[qixiaoyu]

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 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.

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@xxxxxxxxxx>
> >>>>>---
> >>>>>  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);