From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hyunchul Lee Subject: Re: [RFC PATCH 0/2] apply write hints to select the type of segments Date: Mon, 13 Nov 2017 11:25:07 +0900 Message-ID: <5A090283.60206@gmail.com> References: <1510206688-12767-1-git-send-email-hyc.lee@gmail.com> <1b0b44de-c724-5dc4-e9cb-79a894bdb611@huawei.com> <5A04F184.3000204@gmail.com> <5A08E657.8060807@gmail.com> <5A08F6CA.6040507@gmail.com> <5bd3945c-16f8-a718-a140-44589ceb490a@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5bd3945c-16f8-a718-a140-44589ceb490a@huawei.com> Sender: linux-kernel-owner@vger.kernel.org To: Chao Yu , Jaegeuk Kim Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, kernel-team@lge.com, Hyunchul Lee List-Id: linux-f2fs-devel.lists.sourceforge.net 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 >>>>>>>> >>>>>>>> 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. 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 >>>>>> >>>>>> . >>>>>> >>>>> >>>>> >>>> >>>> . >>>> >>> >>> >> >> . >> > >