Attachment 249992 Details for Bug 278375 – EN text (template filled, except for yet missing info)

EN text (template filled, except for yet missing info)

OpenZFS_ARC_pruning.txt (text/plain), 4.56 KB, created by Olivier Certner on 2024-04-15 09:14:00 UTC

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Creator: Olivier Certner

Created: 2024-04-15 09:14:00 UTC

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>=============================================================================
>FreeBSD-EN-ERRATA_TEMPLATE                                      Errata Notice
>                                                          The FreeBSD Project
>
>Topic:          High CPU usage by kernel threads related to ZFS
>
>Category:       contrib
>Module:         zfs
>Announced:      2024-04-1X
>Affects:        FreeBSD 13.x
>Corrected:      2024-04-12 13:00:11 UTC (stable/13, 13-STABLE)
>                2024-04-1X XX:XX:XX UTC (releng/13.3, 13.3-RELEASE-pXX)
>
>For general information regarding FreeBSD Errata Notices and Security
>Advisories, including descriptions of the fields above, security
>branches, and the following sections, please visit
><URL:https://security.FreeBSD.org/>.
>
>I.   Background
>
>ZFS is an advanced and scalable file system originally developed by Sun
>Microsystems for its Solaris operating system. ZFS was integrated as part of
>the FreeBSD starting with FreeBSD 7.0, and it has since become a prominent
>and preferred choice for storage management.
>
>II.  Problem Description
>
>Because ZFS may consume large amounts of RAM to cache various types of
>filesystem objects, it continuously monitors system RAM available to decide
>whether to shrink its caches.  Some caches are shrunk using a dedicated
>thread, to which work is dispatched asynchronously.
>
>In some cases, the cache shrinking logic may dispatch excessive amounts of
>work to the "ARC pruning" thread, causing it to continue attempting to shrink
>caches even after resource shortages are resolved.
>
>III. Impact
>
>The bug manifests as a kernel thread, "arc_prune", consuming 100% of a CPU core
>for indefinite periods, even while the system is otherwise idle.  This behavior
>also impacts workloads running on the system, by reducing available CPU
>resources and by triggering lock contention in the kernel, in particular with
>the "vnlru" process whose function is to recycle vnodes (structures representing
>files, whether opened or cached), a mechanism frequently triggered by intensive
>filesystem workloads.
>
>IV.  Workaround
>
>No workaround is available.  Systems not using ZFS are unaffected.
>
>V.   Solution
>
>Upgrade your system to a supported FreeBSD stable or release / security branch
>(releng) dated after the correction date.  A reboot is required following the
>upgrade.
>
>Perform one of the following:
>
>1) To update your system via a binary patch:
>
>Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms,
>or the i386 platform on FreeBSD 13 and earlier, can be updated via
>the freebsd-update(8) utility:
>
># freebsd-update fetch
># freebsd-update install
># reboot
>
>2) To update your system via a source code patch:
>
>The following patches have been verified to apply to the applicable
>FreeBSD release branches.
>
>a) Download the relevant patch from the location below, and verify the
>detached PGP signature using your PGP utility.
>
>[FreeBSD 13.3]
># fetch https://security.FreeBSD.org/patches/EN-XX:XX/XXXX.patch
># fetch https://security.FreeBSD.org/patches/EN-XX:XX/XXXX.patch.asc
># gpg --verify XXXX.patch.asc
>
>b) Apply the patch.  Execute the following commands as root:
>
># cd /usr/src
># patch < /path/to/patch
>
>c) Recompile your kernel as described in
><URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
>system.
>
>VI.  Correction details
>
>This issue is corrected as of the corresponding Git commit hash or Subversion
>revision number in the following stable and release branches:
>
>Branch/path                             Hash                     Revision
>-------------------------------------------------------------------------
>stable/13/                              330954bdb822    stable/13-n257698
>releng/13.3/                            XXXXXXXXXXXX  releng/13.3-nXXXXXX
>-------------------------------------------------------------------------
>
>Run the following command to see which files were modified by a
>particular commit:
>
># git show --stat <commit hash>
>
>Or visit the following URL, replacing NNNNNN with the hash:
>
><URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>
>
>To determine the commit count in a working tree (for comparison against
>nNNNNNN in the table above), run:
>
># git rev-list --count --first-parent HEAD
>
>VII. References
>
>See problem reports
><URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=274698> and
><URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=275594>.
>
>See also the previous, similar errata notice issued for FreeBSD 14.0:
><URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-23:18.openzfs.asc>.
>
>The latest revision of this advisory is available at
><URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-XX:XX.XXXXX.asc>

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