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. >> >> 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 ;) 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 CURSEG_HOT_NODE WRITE_LIFE_MEDIUM 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
