On 2017/11/13 9:35, Hyunchul Lee wrote: > On 11/13/2017 10:26 AM, Chao Yu wrote: >> On 2017/11/13 8:24, Hyunchul Lee wrote: >>> On 11/10/2017 03:42 PM, Chao Yu wrote: >>>> 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 <[email protected]> >>>>>>> >>>>>>> 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 >>>> >>> >>> I agree, But I am not sure that assigning the same hint to a node and data >>> segment is good. Because NVMe is likely to write them in the same erase >>> block if they have the same hint. >> >> If we do not give the hint, they can still be written to the same erase >> block,
I mean it's possible to write them to the same erase block. :) >> right? it will not be worse? >> > > If the hint is not given, I think that they could be written to > the same erase block, or not. But if we give the same hint, they are written > to the same block. IMO, Only if underlying device can support more hint type or opened channels, and actual temperature of data segment and node segment is quite different, we can separate them. Thanks, > I am not sure ;) > >> Thanks, >> >>> >>> Thanks. >>> >>>> 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 >>>>> >>>>> . >>>>> >>>> >>>> >>> >>> . >>> >> >> > > . >
