Date: Fri, 23 Aug 2019 11:26:28 -0700 From: Matthew Ahrens <mahrens@delphix.com> To: developer <developer@open-zfs.org>, illumos-zfs <zfs@lists.illumos.org>, zfs-devel@list.zfsonlinux.org, zfs-devel@freebsd.org, freebsd-fs <freebsd-fs@freebsd.org>, zfs-discuss <zfs-discuss@zfsonlinux.org> Subject: Re: August OpenZFS Leadership Meeting Message-ID: <CAJjvXiF6XcvGyErhEcosRCmUdejj7%2BgpVjvTHrGVKfCPW-wvyQ@mail.gmail.com> In-Reply-To: <CAJjvXiEZjHiCTZB0ZKyt=nByf5hBo47SsgNzgvvsWPfb-Tik5Q@mail.gmail.com> References: <CAJjvXiE%2B27fYZh-RUmE=mjD4N63TrnTQVb65qaPZDj4K6oS-Rg@mail.gmail.com> <CAJjvXiE7y%2BYXAZCewDKNKXCmvMYhh4Fy0wt8Kh8V21WvYz3opg@mail.gmail.com> <CAJjvXiHhhZcg_4Ju1U1F9UWRxbNyJyDdnxp89CnBCQpWvqO4xw@mail.gmail.com> <CAJjvXiG4xB76c5p6OVmu9-zVz47DCcmPs%2BT0TUvMf572WXtNxw@mail.gmail.com> <CAJjvXiGXzxu0KiJ1eEHpcpM_o-L6zK-Kd=J2QjXC2wQsMR3Szg@mail.gmail.com> <CAJjvXiEE9beZ1fa8ug3SOExZLS6zkprCn%2BYaZRaKb-3WYAo7zA@mail.gmail.com> <CAJjvXiGtdTdHWOb7A10=NkV3NXAvwh14yK2gZv%2BLmW9AJF4zMw@mail.gmail.com> <CAJjvXiEpHq9KufwyUP5-pfJCg4LFcOGhZ5zojeqXdQ5eGAXknQ@mail.gmail.com> <CAJjvXiEZjHiCTZB0ZKyt=nByf5hBo47SsgNzgvvsWPfb-Tik5Q@mail.gmail.com>
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Thanks to everyone who participated at this month's meeting. We discussed OpenZFS DevSummit talks; the Linux Plumbers Conference; 32-bit kernel atomic reads; zfs share -a on Linux; and dedup improvements. The video is available here: https://www.youtube.com/watch?v=3Dzl4CUMOIi18 Notes (thanks Karyn): - OpenZFS DevSummit talks (matt) - Lots of great talks so far, but there is still room. - If you forgot to submit a talk before yesterday=E2=80=99s deadline, p= lease reach out right away. Matt will announce selected speakers in 2 weeks= , so there is a small grace period. - Registration is open now, and Matt will publicize this more once we announce the speakers. - Linux Plumbers conf (Serapheim) - George WIlson and Serapheim will be at the Conference if you want to talk ZFS or Debugging the Linux Kernel - If so, please reach out so the ZFS folks can meet up and talk about all things ZFS. - OpenZFS on 32-bit architectures (relevant for FreeBSD, Linux, =E2=80=A6)= : plain reads of 64-bit =E2=80=9Catomics=E2=80=9D (Andriy) - Issue discovered: We use atomic operations to modify 64-bit values that we treat as atomic, but to read them we use plain C assignment operations, which works ok for 64-bit platforms, but not for 32-bit. Those plain reads are implemented as 2 instructions there (32-bit), which i= s incorrect. - At this point it is mostly theoretical (its is rare to hit a write while crossing the 32-bit boundary) but it is still a valid concern. - The code paths are not very critical - mostly stats that we send to user space. - Proposal for discussion: Should we introduce some kind of format wrappers for those operations? - Paul Dagnelie: Has done some similar work for the SPL back in the day and this should be straightforward. - Question: How many 32-bit platforms do we actually care for at this point? - Andriy: Have heard of a few 32-bit Intel users out there - Tom Caputi: Has some experience for compile-time checks for structures of these nature. - It seems like people are for it. Andriy will first talk with FreeBSD developers, figure out how they want to proceed, and try to propose designs common for all platforms. - zfs share -a (George) - Issue: Stale file handles using zfs share -a and the sharenfs property, by restarting or rebooting the nfs server. - The reason is that ZFS plugs into SystemD in a cumbersome/non-natural way. - NFS shares actually start before the ZFS service. Mountd responds to the client before the ZFS share is actually completed leading to the stale handles. - Hacky Approach: - Introduce a new component to zfs share. Instead of zfs share -a , zfs share -g (short for generate) - The idea is to add ZFS logic that ties it closer to NFS - Change of dependency ordering, zfs share -g generates the handles for NFS, before NFS, and NFS consumes those generated handles. - Cons: A bit hacky for now - Pros: Simple and fast - Plan: To do more redesign on top of this for a cleaner solution - Others that have similar issues with George/Delphix feel free to reach out. - Tom Caputi: Datto had issues with NFS in the past, and don't use sharenfs, but they are interested on having control over th= is functionality - Allan Jude: Seems like FreeBSD already does something similar, so there may be some convergence of goals. - Submitted this as lightning talk at the Dev Summit - Anyone interested in working on implementing Matt=E2=80=99s ideas for de= dup ceiling and on disk format log ( http://open-zfs.org/w/images/8/8d/ZFS_dedup.pdf) please contact allan@klarasystems.com to discuss. (Allan) - Problems using the feature for Terabytes of data due to known memory issues - There is budget for a contract to implement the limit of the size of the DDT proposed during one of the past Dev Summits - Feel free to reach out if you are interested in undertaking that work On Mon, Aug 19, 2019 at 12:56 PM Matthew Ahrens <mahrens@delphix.com> wrote= : > The next OpenZFS Leadership meeting will be held tomorrow, August 20, > 1pm-2pm Pacific time. > > Everyone is welcome to attend and participate, and we will try to keep th= e > meeting on agenda and on time. The meetings will be held online via Zoom= , > and recorded and posted to the website and YouTube after the meeting. > > The agenda for the meeting will be a discussion of the projects listed in > the agenda doc. > > For more information and details on how to attend, as well as notes and > video from the previous meeting, please see the agenda document: > > > https://docs.google.com/document/d/1w2jv2XVYFmBVvG1EGf-9A5HBVsjAYoLIFZAnW= HhV-BM/edit > > --matt >
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