On 2017/11/10 8:23, Hyunchul Lee wrote: > Hello, Chao > > On 11/09/2017 06:12 PM, Chao Yu wrote: >> On 2017/11/9 13:51, Hyunchul Lee wrote: >>> From: Hyunchul Lee <cheol....@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? >> > > I am afraid that this makes side effects. for example, this could cause > out-of-place updates even when there are not enough free segments. > I can write the patch that handles these situations. But I wonder > that this is required, and I am not sure which IPU polices can be disabled.
Oh, As I replied in another thread, I think IPU just affects filesystem hot/cold separating, rather than this feature. So I think it will be okay to not consider it. > >>> >>> 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") >> > > Sure I will. I wrote it already ;) Cool, ;) > I think that datas from the same segment should be passed down with the same > hint, and the following mapping is reasonable. I wonder what is your opinion > about it. > > segment type hints > ------------ ----- > CURSEG_COLD_DATA WRITE_LIFE_EXTREME > CURSEG_HOT_DATA WRITE_LIFE_SHORT > CURSEG_COLD_NODE WRITE_LIFE_NORMAL We have WRITE_LIFE_LONG defined rather than WRITE_LIFE_NORMAL in fs.h? > CURSEG_HOT_NODE WRITE_LIFE_MEDIUM As I know, in scenario of cell phone, data of meta_inode is hottest, then hot data, warm node, and cold node should be coldest. So I suggested we can define as below: META_DATA WRITE_LIFE_SHORT HOT_DATA & WARM_NODE WRITE_LIFE_MEDIUM HOT_NODE & WARM_DATA WRITE_LIFE_LONG COLD_NODE & COLD_DATA WRITE_LIFE_EXTREME Thanks, > others WRITE_LIFE_NONE > >> 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(-) >>> >> >> > > Thanks > > . >
