Spurious warning when setting ARC minimum and maximum values from kernel command line

[BrassyPanache]

System information

Type	Version/Name
Distribution Name	Gentoo
Distribution Version	Stable (it's a rolling release)
Kernel Version	5.10.52
Architecture	amd64
OpenZFS Version	zfs-2.1.0

Issue

When specifying the following kernel parameters to set the ARC size:

zfs.zfs_arc_min=268435456 zfs.zfs_arc_max=1073741824

I receive the following warning:

[    0.043410] WARNING: ignoring tunable zfs_arc_min (using 0 instead)
[    0.043411] WARNING: ignoring tunable zfs_arc_min (using 0 instead)
[    0.043411] WARNING: ignoring tunable zfs_arc_max (using 0 instead)

The warning appears to be spurious because when I check my ARC size it seems to be set to the expected values:

# cat  /proc/spl/kstat/zfs/arcstats | grep -E "c_m[ax|in]"
c_min                           4    268435456
c_max                           4    1073741824

I compile ZFS statically into the kernel (rather than as a module).

My full kernel command line is as follows:

quiet mitigations=off intel_pstate=disable nosmt zfs.zfs_arc_min=268435456 zfs.zfs_arc_max=1073741824

This log message caused me some confusion and I spent some time investigating the apparent failure.

Thanks for all the efforts.

[paulhargreaves]

Please see #10157 (comment)

[itspngu]

In my case the message¹ disappears when setting zfs_arc_max before zfs_arc_min. Tripped over it when skimming through the dmesg of my Proxmox host. My guess is that the defaults have been tampered with so setting zfs_arc_min first fails because it's larger than zfs_arc_max.

¹ I was getting 2 consecutive lines of ignoring tunable zfs_arc_min (using 0 instead) on boot until I swapped the order around in /etc/modprobe.d/zfs.conf.

[BrassyPanache]

Thanks @paulhargreaves for that link. I've just testing again using release 2.1.2. The error for me still remains.

Thanks @itspngu. I've tried both min before max and max before min to no avail.

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