On 2017/11/14 12:20, Jaegeuk Kim wrote: > On 11/13, Hyunchul Lee wrote: >> On 11/13/2017 10:59 AM, Chao Yu wrote: >>> 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 <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 >>>>>>> >>>>>> >>>>>> 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. >>> >> >> Okay, If Jaegeuk Kim agrees with this, I will submit the patch that >> implements your proposed mapping. > > How about this? We'd better to split data and node blocks as much as possible. > > segment type hints > ------------ ----- > COLD_NODE & COLD_DATA WRITE_LIFE_NONE
WRITE_LIFE_NONE means there is no hints about write life time. Shouldn't we define COLD_NODE & COLD_DATA as WRITE_LIFE_EXTERME? Thanks, > WARM_DATA WRITE_LIFE_EXTERME > HOT_NODE & WARM_NODE WRITE_LIFE_LONG > HOT_DATA WRITE_LIFE_MEDIUM > META_DATA WRITE_LIFE_SHORT > >> >> Thank you for comments ;) >> >>> 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 >>>>>>>> >>>>>>>> . >>>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> . >>>>>> >>>>> >>>>> >>>> >>>> . >>>> >>> >>> > > . >
