From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: RE: [PATCH 00/16] f2fs: introduce flash-friendly file system Date: Tue, 09 Oct 2012 19:45:57 +0900 Message-ID: <007c01cda60b$43e7fae0$cbb7f0a0$%kim@samsung.com> References: <415E76CC-A53D-4643-88AB-3D7D7DC56F98@dubeyko.com> <9DE65D03-D4EA-4B32-9C1D-1516EAE50E23@dubeyko.com> <1349553966.12699.132.camel@kjgkr> <50712AAA.5030807@gmail.com> <002201cda46e$88b84d30$9a28e790$%kim@samsung.com> <004101cda52e$72210e20$56632a60$%kim@samsung.com> <004a01cda542$f398e2c0$dacaa840$%kim@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: 'Namjae Jeon' , 'Vyacheslav Dubeyko' , 'Marco Stornelli' , 'Jaegeuk Kim' , 'Al Viro' , tytso@mit.edu, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, chur.lee@samsung.com, cm224.lee@samsung.com, jooyoung.hwang@samsung.com, linux-fsdevel@vger.kernel.org To: =?utf-8?Q?'Luk=C3=A1=C5=A1_Czerner'?= Return-path: Received: from mailout3.samsung.com ([203.254.224.33]:12805 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751535Ab2JIKqR convert rfc822-to-8bit (ORCPT ); Tue, 9 Oct 2012 06:46:17 -0400 In-reply-to: Content-language: ko Sender: linux-fsdevel-owner@vger.kernel.org List-ID: > -----Original Message----- > From: linux-fsdevel-owner@vger.kernel.org [mailto:linux-fsdevel-owner= @vger.kernel.org] On Behalf Of > Luka? Czerner > Sent: Tuesday, October 09, 2012 5:32 PM > To: Jaegeuk Kim > Cc: 'Namjae Jeon'; 'Vyacheslav Dubeyko'; 'Marco Stornelli'; 'Jaegeuk = Kim'; 'Al Viro'; tytso@mit.edu; > gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; chur.lee@sa= msung.com; cm224.lee@samsung.com; > jooyoung.hwang@samsung.com; linux-fsdevel@vger.kernel.org > Subject: RE: [PATCH 00/16] f2fs: introduce flash-friendly file system >=20 > On Mon, 8 Oct 2012, Jaegeuk Kim wrote: >=20 > > Date: Mon, 08 Oct 2012 19:52:03 +0900 > > From: Jaegeuk Kim > > To: 'Namjae Jeon' > > Cc: 'Vyacheslav Dubeyko' , > > 'Marco Stornelli' , > > 'Jaegeuk Kim' , > > 'Al Viro' , tytso@mit.edu, > > gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, > > chur.lee@samsung.com, cm224.lee@samsung.com, jooyoung.hwang@sam= sung.com, > > linux-fsdevel@vger.kernel.org > > Subject: RE: [PATCH 00/16] f2fs: introduce flash-friendly file syst= em > > > > > -----Original Message----- > > > From: Namjae Jeon [mailto:linkinjeon@gmail.com] > > > Sent: Monday, October 08, 2012 7:00 PM > > > To: Jaegeuk Kim > > > Cc: Vyacheslav Dubeyko; Marco Stornelli; Jaegeuk Kim; Al Viro; ty= tso@mit.edu; > > > gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; chur.le= e@samsung.com; > cm224.lee@samsung.com; > > > jooyoung.hwang@samsung.com; linux-fsdevel@vger.kernel.org > > > Subject: Re: [PATCH 00/16] f2fs: introduce flash-friendly file sy= stem > > > > > > 2012/10/8, Jaegeuk Kim : > > > >> -----Original Message----- > > > >> From: Vyacheslav Dubeyko [mailto:slava@dubeyko.com] > > > >> Sent: Sunday, October 07, 2012 9:09 PM > > > >> To: Jaegeuk Kim > > > >> Cc: 'Marco Stornelli'; 'Jaegeuk Kim'; 'Al Viro'; tytso@mit.edu= ; > > > >> gregkh@linuxfoundation.org; linux- > > > >> kernel@vger.kernel.org; chur.lee@samsung.com; cm224.lee@samsun= g.com; > > > >> jooyoung.hwang@samsung.com; > > > >> linux-fsdevel@vger.kernel.org > > > >> Subject: Re: [PATCH 00/16] f2fs: introduce flash-friendly file= system > > > >> > > > >> Hi, > > > >> > > > >> On Oct 7, 2012, at 1:31 PM, Jaegeuk Kim wrote: > > > >> > > > >> >> -----Original Message----- > > > >> >> From: Marco Stornelli [mailto:marco.stornelli@gmail.com] > > > >> >> Sent: Sunday, October 07, 2012 4:10 PM > > > >> >> To: Jaegeuk Kim > > > >> >> Cc: Vyacheslav Dubeyko; jaegeuk.kim@samsung.com; Al Viro; > > > >> >> tytso@mit.edu; gregkh@linuxfoundation.org; > > > >> >> linux-kernel@vger.kernel.org; chur.lee@samsung.com; > > > >> >> cm224.lee@samsung.com; > > > >> jooyoung.hwang@samsung.com; > > > >> >> linux-fsdevel@vger.kernel.org > > > >> >> Subject: Re: [PATCH 00/16] f2fs: introduce flash-friendly f= ile system > > > >> >> > > > >> >> Il 06/10/2012 22:06, Jaegeuk Kim ha scritto: > > > >> >>> 2012-10-06 (=ED=86=A0), 17:54 +0400, Vyacheslav Dubeyko: > > > >> >>>> Hi Jaegeuk, > > > >> >>> > > > >> >>> Hi. > > > >> >>> We know each other, right? :) > > > >> >>> > > > >> >>>> > > > >> >>>>> From: =EA=B9=80=EC=9E=AC=EA=B7=B9 > > > >> >>>>> To: viro@zeniv.linux.org.uk, 'Theodore Ts'o' , > > > >> >> gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, > > > >> >> chur.lee@samsung.com, > > > >> cm224.lee@samsung.com, > > > >> >> jaegeuk.kim@samsung.com, jooyoung.hwang@samsung.com > > > >> >>>>> Subject: [PATCH 00/16] f2fs: introduce flash-friendly = file system > > > >> >>>>> Date: Fri, 05 Oct 2012 20:55:07 +0900 > > > >> >>>>> > > > >> >>>>> This is a new patch set for the f2fs file system. > > > >> >>>>> > > > >> >>>>> What is F2FS? > > > >> >>>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > >> >>>>> > > > >> >>>>> NAND flash memory-based storage devices, such as SSD, eM= MC, and SD > > > >> >>>>> cards, have > > > >> >>>>> been widely being used for ranging from mobile to server= systems. > > > >> >>>>> Since they are > > > >> >>>>> known to have different characteristics from the convent= ional > > > >> >>>>> rotational disks, > > > >> >>>>> a file system, an upper layer to the storage device, sho= uld adapt to > > > >> >>>>> the changes > > > >> >>>>> from the sketch. > > > >> >>>>> > > > >> >>>>> F2FS is a new file system carefully designed for the NAN= D flash > > > >> >>>>> memory-based storage > > > >> >>>>> devices. We chose a log structure file system approach, = but we tried > > > >> >>>>> to adapt it > > > >> >>>>> to the new form of storage. Also we remedy some known is= sues of the > > > >> >>>>> very old log > > > >> >>>>> structured file system, such as snowball effect of wande= ring tree > > > >> >>>>> and high cleaning > > > >> >>>>> overhead. > > > >> >>>>> > > > >> >>>>> Because a NAND-based storage device shows different char= acteristics > > > >> >>>>> according to > > > >> >>>>> its internal geometry or flash memory management scheme = aka FTL, we > > > >> >>>>> add various > > > >> >>>>> parameters not only for configuring on-disk layout, but = also for > > > >> >>>>> selecting allocation > > > >> >>>>> and cleaning algorithms. > > > >> >>>>> > > > >> >>>> > > > >> >>>> What about F2FS performance? Could you share benchmarking= results of > > > >> >>>> the new file system? > > > >> >>>> > > > >> >>>> It is very interesting the case of aged file system. How = is GC's > > > >> >>>> implementation efficient? Could > > > >> >> you share benchmarking results for the very aged file syste= m state? > > > >> >>>> > > > >> >>> > > > >> >>> Although I have benchmark results, currently I'd like to s= ee the > > > >> >>> results > > > >> >>> measured by community as a black-box. As you know, the res= ults are > > > >> >>> very > > > >> >>> dependent on the workloads and parameters, so I think it w= ould be > > > >> >>> better > > > >> >>> to see other results for a while. > > > >> >>> Thanks, > > > >> >>> > > > >> >> > > > >> >> 1) Actually it's a strange approach. If you have got any re= sults you > > > >> >> should share them with the community explaining how (the wo= rkload, hw > > > >> >> and so on) your benchmark works and the specific condition.= I really > > > >> >> don't like the approach "I've got the results but I don't s= ay > > > >> >> anything, > > > >> >> if you want a number, do it yourself". > > > >> > > > > >> > It's definitely right, and I meant *for a while*. > > > >> > I just wanted to avoid arguing with how to age file system i= n this > > > >> > time. > > > >> > Before then, I share the primitive results as follows. > > > >> > > > > >> > 1. iozone in Panda board > > > >> > - ARM A9 > > > >> > - DRAM : 1GB > > > >> > - Kernel: Linux 3.3 > > > >> > - Partition: 12GB (64GB Samsung eMMC) > > > >> > - Tested on 2GB file > > > >> > > > > >> > seq. read, seq. write, rand. read, rand. write > > > >> > - ext4: 30.753 17.066 5.06 4.15 > > > >> > - f2fs: 30.71 16.906 5.073 15.204 > > > >> > > > > >> > 2. iozone in Galaxy Nexus > > > >> > - DRAM : 1GB > > > >> > - Android 4.0.4_r1.2 > > > >> > - Kernel omap 3.0.8 > > > >> > - Partition: /data, 12GB > > > >> > - Tested on 2GB file > > > >> > > > > >> > seq. read, seq. write, rand. read, rand. write > > > >> > - ext4: 29.88 12.83 11.43 0.56 > > > >> > - f2fs: 29.70 13.34 10.79 12.82 > > > >> > > > > >> > > > >> > > > >> This is results for non-aged filesystem state. Am I correct? > > > >> > > > > > > > > Yes, right. > > > > > > > >> > > > >> > Due to the company secret, I expect to show other results af= ter > > > >> > presenting f2fs at korea linux forum. > > > >> > > > > >> >> 2) For a new filesystem you should send the patches to linu= x-fsdevel. > > > >> > > > > >> > Yes, that was totally my mistake. > > > >> > > > > >> >> 3) It's not clear the pros/cons of your filesystem, can you= share with > > > >> >> us the main differences with the current fs already in main= line? Or is > > > >> >> it a company secret? > > > >> > > > > >> > After forum, I can share the slides, and I hope they will be= useful to > > > >> > you. > > > >> > > > > >> > Instead, let me summarize at a glance compared with other fi= le systems. > > > >> > Here are several log-structured file systems. > > > >> > Note that, F2FS operates on top of block device with conside= ration on > > > >> > the FTL behavior. > > > >> > So, JFFS2, YAFFS2, and UBIFS are out-of scope, since they ar= e designed > > > >> > for raw NAND flash. > > > >> > LogFS is initially designed for raw NAND flash, but expanded= to block > > > >> > device. > > > >> > But, I don't know whether it is stable or not. > > > >> > NILFS2 is one of major log-structured file systems, which su= pports > > > >> > multiple snap-shots. > > > >> > IMO, that feature is quite promising and important to users,= but it may > > > >> > degrade the performance. > > > >> > There is a trade-off between functionalities and performance= =2E > > > >> > F2FS chose high performance without any further fancy functi= onalities. > > > >> > > > > >> > > > >> Performance is a good goal. But fault-tolerance is also very i= mportant > > > >> point. Filesystems are used by > > > >> users, so, it is very important to guarantee reliability of da= ta keeping. > > > >> Degradation of performance > > > >> by means of snapshots is arguable point. Snapshots can solve t= he problem > > > >> not only some unpredictable > > > >> environmental issues but also user's erroneous behavior. > > > >> > > > > > > > > Yes, I agree. I concerned the multiple snapshot feature. > > > > Of course, fault-tolerance is very important, and file system s= hould support > > > > it as you know as power-off-recovery. > > > > f2fs supports the recovery mechanism by adopting checkpoint sim= ilar to > > > > snapshot. > > > > But, f2fs does not support multiple snapshots for user convenie= nce. > > > > I just focused on the performance, and absolutely, the multiple= snapshot > > > > feature is also a good alternative approach. > > > > That may be a trade-off. > > > > > > > >> As I understand, it is not possible to have a perfect performa= nce in all > > > >> possible workloads. Could you > > > >> point out what workloads are the best way of F2FS using? > > > > > > > > Basically I think the following workloads will be good for F2FS= =2E > > > > - Many random writes : it's LFS nature > > > > - Small writes with frequent fsync : f2fs is optimized to reduc= e the fsync > > > > overhead. > > > > > > > >> > > > >> > Maybe or obviously it is possible to optimize ext4 or btrfs = to flash > > > >> > storages. > > > >> > IMHO, however, they are originally designed for HDDs, so tha= t it may or > > > >> > may not suffer from > > > >> fundamental designs. > > > >> > I don't know, but why not designing a new file system for fl= ash storages > > > >> > as a counterpart? > > > >> > > > > >> > > > >> Yes, it is possible. But F2FS is not flash oriented filesystem= as JFFS2, > > > >> YAFFS2, UBIFS but block- > > > >> oriented filesystem. So, F2FS design is restricted by block-la= yer's > > > >> opportunities in the using of > > > >> flash storages' peculiarities. Could you point out key points = of F2FS > > > >> design that makes this design > > > >> fundamentally unique? > > > > > > > > As you can see the f2fs kernel document patch, I think one of t= he most > > > > important features is to align operating units between f2fs and= ftl. > > > > Specifically, f2fs has section and zone, which are cleaning uni= t and basic > > > > allocation unit respectively. > > > > Through these configurable units in f2fs, I think f2fs is able = to reduce the > > > > unnecessary operations done by FTL. > > > > And, in order to avoid changing IO patterns by the block-layer,= f2fs merges > > > > itself some bios likewise ext4. > > > Hello. > > > The internal of eMMC and SSD is the blackbox from user side. > > > How does the normal user easily set operating units alignment(pag= e > > > size and physical block size ?) between f2fs and ftl in storage d= evice > > > ? > > > > I've known that some works have been tried to figure out the units = by profiling the storage, AKA > reverse engineering. > > In most cases, the simplest way is to measure the latencies of cons= ecutive writes and analyze their > patterns. > > As you mentioned, in practical, users will not want to do this, so = maybe we need a tool to profile > them to optimize f2fs. > > In the current state, I think profiling is an another issue, and mk= fs.f2fs had better include this > work in the future. > > But, IMO, from the viewpoint of performance, default configuration = is quite enough now. > > > > ps) f2fs doesn't care about the flash page size, but considers garb= age collection unit. >=20 > I am sorry but this reply makes me smile. How can you design a fs > relying on time attack heuristics to figure out what the proper > layout should be ? Or even endorse such heuristics to be used in > mkfs ? What we should be focusing on is to push vendors to actually > give us such information so we can properly propagate that > throughout the kernel - that's something everyone will benefit from. > After that the optimization can be done in every file system. >=20 =46rankly speaking, I agree that it would be the right direction eventu= ally. But, as you know, it's very difficult for all flash vendors to promote = and standardize that. Because each vendors have different strategies to open their internal i= nformation and also try to protect their secrets whatever they are. IMO, we don't need to wait them now. Instead, from the start, I suggest f2fs that uses those information to = the file system design. In addition, I suggest using heuristics right now as best efforts. Maybe in future, if vendors give something, f2fs would be more feasible= =2E In the mean time, I strongly hope to validate and stabilize f2fs with c= ommunity. > Promoting time attack heuristics instead of pushing vendors to tell > us how their hardware should be used is a journey to hell and we've > been talking about this for a looong time now. And I imagine that > you especially have quite some persuasion power. I know. :) If there comes a chance, I want to try. Thanks, >=20 > Thanks! > -Lukas >=20 > > > > > > > > Thanks. > > > > > > > > > > >> > > > >> With the best regards, > > > >> Vyacheslav Dubeyko. > > > >> > > > >> > > > >> >> > > > >> >> Marco > > > >> > > > > >> > --- > > > >> > Jaegeuk Kim > > > >> > Samsung > > > >> > > > > >> > -- > > > >> > To unsubscribe from this list: send the line "unsubscribe li= nux-kernel" > > > >> > in > > > >> > the body of a message to majordomo@vger.kernel.org > > > >> > More majordomo info at http://vger.kernel.org/majordomo-inf= o.html > > > >> > Please read the FAQ at http://www.tux.org/lkml/ > > > > > > > > > > > > --- > > > > Jaegeuk Kim > > > > Samsung > > > > > > > > -- > > > > To unsubscribe from this list: send the line "unsubscribe linux= -fsdevel" in > > > > the body of a message to majordomo@vger.kernel.org > > > > More majordomo info at http://vger.kernel.org/majordomo-info.h= tml > > > > > > > > > > --- > > Jaegeuk Kim > > Samsung > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-fsd= evel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > --- Jaegeuk Kim Samsung -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html