Setting sysctl vfs.zfs.arc_max failed: 22

[Nathan Bosley]

I was just testing this a bit.
I can now set max in loader.conf as expected.

I did notice one thing that I thought was a bit strange though.

As a reference, here are my defaults without any ARC tunables/sysctls:

vfs.zfs.arc_meta_limit: 3903459328
vfs.zfs.arc_min: 1951729664
vfs.zfs.arc_max: 15613837312

If I put vfs.zfs.arc_max="8589934592" in loader.conf, the results are:

vfs.zfs.arc_meta_limit: 2147483648
vfs.zfs.arc_min: 1073741824
vfs.zfs.arc_max: 8589934592

So meta_limit and min are also changed, which is reasonable.

If I remove all of my ARC tunables in loader.conf, so that I have the
default values after booting, and then use:
# sysctl vfs.zfs.arc_max="8589934592"

The result is:

vfs.zfs.arc_meta_limit: 2147483648
vfs.zfs.arc_min: 1951729664
vfs.zfs.arc_max: 8589934592

Max was set as requested.
meta_limit was set to max/4.
But min is still at the default.

In other words, if I use loader.conf to set max, then min and meta_limit
are also recalculated.
But if I use sysctl to set max, only meta_limit is recalculated; min
remains at the default.
I'm not sure if that's the intent.

Just a heads-up.

Thanks again.

On Wed, Jul 6, 2016 at 7:51 PM, Steven Hartland <killing at multiplay.co.uk>
wrote:

> On 06/07/2016 21:39, Eric van Gyzen wrote:
>
>> On 07/06/16 03:35 PM, Steven Hartland wrote:
>>
>>> The ARC settings and kmem aren't initialised when tunables are loaded
>>> so the tests fail.
>>>
>>> I've fixed this locally by blindly setting if ARC is not configured.
>>> Request to commit the fix is with re@
>>>
>>> In the mean time the patch is attached.
>>>
>>> Thanks for the report and sorry about the breakage.
>>>
>> No worries.  Thanks for the quick fix.
>>
>> https://svnweb.freebsd.org/changeset/base/302382
>
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