The `zfs_arc_max` setting *is* respected when I set it to a value of `1073741824` = 1GiB
``` cat /etc/modprobe.d/zfs.conf; cat /sys/module/zfs/parameters/zfs_arc_max; cat /proc/spl/kstat/zfs/arcstats |grep ^size -B3 options zfs zfs_arc_max=1073741824 1073741824 c 4 1073741824 c_min 4 519804800 c_max 4 1073741824 size 4 1086124448 ``` The manpage `man zfs-module-parameters` says ``` zfs_arc_max (ulong) Max arc size of ARC in bytes. If set to 0 then it will consume 1/2 of system RAM. This value must be at least 67108864 (64 megabytes). This value can be changed dynamically with some caveats. It cannot be set back to 0 while running and reducing it below the current ARC size will not cause the ARC to shrink without memory pressure to induce shrinking. Default value: 0. ``` Before I had set it to `134217728`, more than 64MiB, but it was not respected. I also tried setting `zfs_arc_max` to `519804800` (495.7MiB, where ever this number comes from), the value reported as `c_min` and it *not* respected. So, the minimum arc size seems to be around 1GB and *not* 64MB, as the manpage claims. (documentation lies, the code does not) -- 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/1854480 Title: zfs_arc_max not working anymore in zfs 0.8.1 Status in zfs-linux package in Ubuntu: Fix Released Bug description: In the past I could limit the size of L1ARC by specifying "options zfs zfs_arc_max=3221225472" in /etc/modprobe.d/zfs.conf. I tried even to fill /sys/module/zfs/parameters/zfs_arc_max directly, but none of those methods limits the size of L1ARC. It worked nicely in zfs 0.7.x. Nowadays I use a nvme drive with 3400 MB/s read throughput and I see not much difference between e.g booting the system from nvme and rebooting the system from L1ARC. Having a 96-99% hit rate for the L1ARC, I like to free up some memory, thus avoiding some delay of freeing memory from L1ARC while loading a VM. ------------------------------------------------------------------------- UPDATE: The system only limits the L1ARC, if we directly after the login write the zfs_arc_max value to the file /sys/module/zfs/parameters/zfs_arc_max. ------------------------------------------------------------------------ ProblemType: Bug DistroRelease: Ubuntu 19.10 Package: zfsutils-linux 0.8.1-1ubuntu14.1 ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7 Uname: Linux 5.3.0-23-generic x86_64 NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair ApportVersion: 2.20.11-0ubuntu8.2 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Fri Nov 29 06:19:15 2019 InstallationDate: Installed on 2019-11-25 (3 days ago) InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017) SourcePackage: zfs-linux UpgradeStatus: No upgrade log present (probably fresh install) modified.conffile..etc.sudoers.d.zfs: [inaccessible: [Errno 13] Permission denied: '/etc/sudoers.d/zfs'] To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1854480/+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
