Hello, I just wanted to clarify the changes in the two commits that were backported. For commit 36a6e2335c45, the main features that were backported were the warnings generated when ARC fails to set the max and min value to the user specified values. Although this commit has a fix for the zfs_arc_max size below allmem/32, it does have a major regression where the issue gets essentially flipped and will cause zfs_arc_min not to accept any value above allmem/2.
Commit e945e8d7f4fc although mainly a FreeBSD patch, does fix the regression created by the previous commit and assures that the user cannot set the value of zfs_arc_max below the maximum transaction size of 64MB. All other FreeBSD specific changes were ignored. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to zfs-linux in Ubuntu. https://bugs.launchpad.net/bugs/1964992 Title: ZFS ignores ARC sizes below allmem/32 Status in zfs-linux package in Ubuntu: Fix Released Status in zfs-linux source package in Bionic: Fix Released Status in zfs-linux source package in Focal: In Progress Bug description: [Impact] ZFS ignores tunable "zfs_arc_max" due to it being below allmem/32 threshold. This prevents users from properly restraining ARC sizes, and can cause increased memory contention in some systems. [Test Plan] 1. Deploy test system with ZFS storage and 32GB RAM 2. Add ARC tunables to /etc/modprobe.d/99-zfs-arc.conf # cat /etc/modprobe.d/99-zfs-arc.conf options zfs zfs_arc_min=536870912 options zfs zfs_arc_max=966367641 3. Reboot system 4. Verify ARC sizes through "arc_summary" # arc_summary | grep -A3 "ARC size" ARC size (current): < 0.1 % 1.3 MiB Target size (adaptive): 100.0 % 15.7 GiB Min size (hard limit): 3.2 % 512.0 MiB Max size (high water): 31:1 15.7 GiB For a 32GB test system, we should be able to set max ARC sizes below 1GB. [Fix] This has been fixed by upstream commit: - 36a6e2335c45 "Don't ignore zfs_arc_max below allmem/32" - e945e8d7f4fc "Restore FreeBSD sysctl processing for arc.min and arc.max" The commit has been introduced in upstream zfs-2.0.0, so it's needed for Bionic and Focal. Releases starting with Impish already have this commit by default: $ git describe --contains 36a6e2335c45 zfs-2.0.0-rc1~332 $ rmadison zfs-linux zfs-linux | 0.7.5-1ubuntu15 | bionic | source zfs-linux | 0.7.5-1ubuntu16.12 | bionic-updates | source zfs-linux | 0.8.3-1ubuntu12 | focal | source zfs-linux | 0.8.3-1ubuntu12.9 | focal-security | source zfs-linux | 0.8.3-1ubuntu12.13 | focal-updates | source zfs-linux | 0.8.3-1ubuntu12.14 | focal-proposed | source zfs-linux | 2.0.6-1ubuntu2 | impish | source zfs-linux | 2.0.6-1ubuntu2.1 | impish-updates | source zfs-linux | 2.1.2-1ubuntu3 | jammy | source [Regression Potential] The introduced commit essentially removes the limitation of setting ARC tunables below allmem/32, and re-arranges the order of how some of the tunables are parsed. Regressions would possibly show up as other tunables being ignored or not being set correctly due to parsing errors. We should validate whether other ARC related tunables are still being set correctly, and whether ZFS is using the set values for the ARC memory thresholds. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1964992/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
