How to setup zfs kernel parameters?

[olivier-norture]

Hey there!

How to setup kernel parameters for ZFS?

I'm trying to adjust zfs arc size using zfs_arc_max (https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#zfs-arc-max).

So I updated my Talos Image to include the parameter:

customization:
  extraKernelArgs:
    - talos.platform=metal
    - cpufreq.default_governor=powersave
    - amd_pstate=active
    - zfs_arc_max=32212254720 # 30GB
  systemExtensions:
    officialExtensions:
      - siderolabs/nvidia-container-toolkit-production
      - siderolabs/nvidia-open-gpu-kernel-modules-production
      - siderolabs/zfs

And I can see that parameter is active:

talosctl -e 192.168.1.49 -n 192.168.1.49 read /proc/cmdline

talos.platform=metal talos.config=none console=tty0 init_on_alloc=1 slab_nomerge pti=on consoleblank=0 nvme_core.io_timeout=4294967295 printk.devkmsg=on ima_template=ima-ng ima_appraise=fix ima_hash=sha512 selinux=1 cpufreq.default_governor=powersave amd_pstate=active zfs_arc_max=32212254720

But the value doesn't respect the setting; it's 60GB at the moment (and keep growing).
Unfortunatly this server run a tons of container as well and when workload increase there is some freeze until ARC release some memory.

Thank you!