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SubjectRe: [RFC PATCH 0/2] apply write hints to select the type of segments
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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?

>
> 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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