Date: Tue, 24 Jun 2025 09:55:33 GMT From: Lorenzo Salvadore <salvadore@FreeBSD.org> To: doc-committers@FreeBSD.org, dev-commits-doc-all@FreeBSD.org Subject: git: 8f8e975c79 - main - Status/2025Q2/packrat.adoc: Add report Message-ID: <202506240955.55O9tXPK026883@gitrepo.freebsd.org>
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The branch main has been updated by salvadore: URL: https://cgit.FreeBSD.org/doc/commit/?id=8f8e975c798a328e9b7985bce6e812c6a3193e01 commit 8f8e975c798a328e9b7985bce6e812c6a3193e01 Author: Rick Macklem <rmacklem@FreeBSD.org> AuthorDate: 2025-06-24 09:50:39 +0000 Commit: Lorenzo Salvadore <salvadore@FreeBSD.org> CommitDate: 2025-06-24 09:51:49 +0000 Status/2025Q2/packrat.adoc: Add report Reviewed by: status (Pau Amma <pauamma@gundo.com>) --- .../en/status/report-2025-04-2025-06/packrat.adoc | 23 ++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/website/content/en/status/report-2025-04-2025-06/packrat.adoc b/website/content/en/status/report-2025-04-2025-06/packrat.adoc new file mode 100644 index 0000000000..7ceaaebd22 --- /dev/null +++ b/website/content/en/status/report-2025-04-2025-06/packrat.adoc @@ -0,0 +1,23 @@ +=== Packrat - NFS client caching on non-volatile storage + +Contact: Rick Macklem <rmacklem@freebsd.org> + +NFSv4.1/4.2 provides support for a feature called delegations. +When a NFSv4.1/4.2 client holds a delegation, the client has certain rights to a file, including a guarantee that no other client will make changes to the file unless the delegation is recalled. +As such, when a client holds a delegation for a file, it can agressively cache the file's data, knowing that it will not be modified by other clients until it returns the delegation. + +This project is intended to allow the NFSv4.1/4.2 client to agressively cache file data on client local non-volatile storage, when the client holds a delegation for the file. +I created a patch long ago to try and do this for NFSv4.0, but it was never at a stage where it was worth using. +This project is a complete rewrite of the patch, done in part because NFSv4.1/4.2 plus other recent NFSv4 related changes makes doing this more feasible. + +The patch is getting stable now, but I am not sure if it will be ready for inclusion in FreeBSD 15 as an experimental feature enabled via a new mount option called "packrat". + +The main thing I still need to do is code a writeback kernel thread. +Right now, dirty chunks stored on client local non-volatile storage get written back to the NFSv4.1/4.2 server upon umount. +This can result in the umount taking a long time (as in many minutes). +To alleviate this, I am planning on implementing a writeback kernel process that will walk the non-volatile storage and write the dirty chunks back. +The trick is to make it aggressive enough that most dirty chunks have been written back when a umount is done, but not so aggressive that it impedes the performance of synchronous NFSv4.1/4.2 RPCs. + +This will be very much an experimental feature, but it is hoped it will allow NFS mounts to be used more effectively, particularily in WAN situations, such as a mobile laptop. + +There is still work to be done, particularily with respect to recovery of delegations after a NFSv4.1/4.2 client restart.
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