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SubjectRe: [RFC PATCH 0/2] apply write hints to select the type of segments
On 11/09, Chao Yu wrote:
> On 2017/11/9 13:51, Hyunchul Lee wrote:
> > From: Hyunchul Lee <cheol.lee@lge.com>
> >
> > Using write hints[1], applications can inform the life time of the data
> > written to devices. and this[2] reported that the write hints patch
> > decreased writes in NAND by 25%.
> >
> > This hints help F2FS to determine the followings.
> > 1) the segment types where the data will be written.
> > 2) the hints that will be passed down to devices with the data of segments.
> >
> > This patch set implements the first mapping from write hints to segment types
> > as shown below.
> >
> > hints segment type
> > ----- ------------
> > WRITE_LIFE_SHORT CURSEG_COLD_DATA
> > WRITE_LIFE_EXTREME CURSEG_HOT_DATA
> > others CURSEG_WARM_DATA
> >
> > The F2FS poliy for hot/cold seperation has precedence over this hints, And
> > hints are not applied in in-place update.
>
> Could we change to disable IPU if file/inode write hint is existing?

Well, this is a hint which is not related to IPU. I think user should be aware
of controlling IPU.

> >
> > Before the second mapping is implemented, write hints are not passed down
> > to devices. Because it is better that the data of a segment have the same
> > hint.
> >
> > [1]: c75b1d9421f80f4143e389d2d50ddfc8a28c8c35
> > [2]: https://lwn.net/Articles/726477/
>
> Could you write a patch to support passing write hint to block layer for
> buffered writes as below commit:
> 0127251c45ae ("ext4: add support for passing in write hints for buffered writes")
>
> Thanks,
>
> >
> > Hyunchul Lee (2):
> > f2fs: apply write hints to select the type of segments for buffered
> > write
> > f2fs: apply write hints to select the type of segment for direct write
> >
> > fs/f2fs/data.c | 101 ++++++++++++++++++++++++++++++++----------------------
> > fs/f2fs/f2fs.h | 1 +
> > fs/f2fs/segment.c | 14 +++++++-
> > 3 files changed, 74 insertions(+), 42 deletions(-)
> >

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