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 10:35:06 +0900 Message-ID: <5A08F6CA.6040507@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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-2.v28.ch3.sourceforge.com ([172.29.28.192] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eE3eh-0007Mf-PI for linux-f2fs-devel@lists.sourceforge.net; Mon, 13 Nov 2017 01:35:19 +0000 Received: from lgeamrelo13.lge.com ([156.147.23.53]) by sfi-mx-2.v28.ch3.sourceforge.com with esmtp (Exim 4.89) id 1eE3ef-0002pA-Gj for linux-f2fs-devel@lists.sourceforge.net; Mon, 13 Nov 2017 01:35:19 +0000 In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu Cc: kernel-team@lge.com, Jaegeuk Kim , Hyunchul Lee , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net 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, > 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. 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 >>>> >>>> . >>>> >>> >>> >> >> . >> > > ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot