ZFS ARC being limited below what is defined in /boot/loader.conf

[Steve Polyack]

This was indeed the issue.  I read your first response incorrectly.  
Thanks a bunch!

On 2/12/2010 4:10 PM, Artem Belevich wrote:
> vm.kmem_size_max/vm.kmem_size_min define the range vm.kmem_size can be set to.
> vm_kmem_size specifies the actual kmem size.
>
> ARC size in turn limited by vm.kmem_size.
>
> If you want to bump ARC size, you do need to bump vm.kmem_size.
>
> --Artem
>
>
>
> On Fri, Feb 12, 2010 at 11:36 AM, Steve Polyack<korvus at comcast.net>  wrote:
>    
>> On 02/12/10 13:47, Artem Belevich wrote:
>>      
>>> On Fri, Feb 12, 2010 at 10:31 AM, Steve Polyack<korvus at comcast.net>
>>>   wrote:
>>>
>>>
>>>        
>>>> Has anyone had an issue with the ZFS ARC max being limited below what has
>>>> been defined in /boot/loader.conf?  I just upgraded the RAM in a
>>>> ZFS-equipped system and attempted to devote 4GB to the ARC cache by
>>>> placing
>>>> the following in loader.conf:
>>>>   vfs.zfs.arc_max="4096M"
>>>>
>>>> However, after rebooting, querying the sysctl gives me this:
>>>> $ sysctl vfs.zfs.arc_max
>>>> vfs.zfs.arc_max: 1726489600
>>>>
>>>> or about 1.7GB, an odd number that I can't find any references to.  For
>>>> reference, I'm running 8-STABLE (as of Jan 19th) on an amd64 system with
>>>> 8GB
>>>> of RAM.  The system was previously very stable with 4GB of RAM and a
>>>> 512MB
>>>> arc_max.  I have not modified vm.kmem_size_max (defaults to ~330GB on
>>>> amd64)
>>>> or any other ZFS tunables.  I'd also like to avoid syncing up to the
>>>> current
>>>> 8-STABLE if at all possible.
>>>>
>>>> Thanks,
>>>> Steve Polyack
>>>>
>>>> _______________________________________________
>>>> freebsd-stable at freebsd.org mailing list
>>>> http://lists.freebsd.org/mailman/listinfo/freebsd-stable
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>>>>
>>>>
>>>>          
>>> Check your vm.kmem_size. Default setting is way too low. Set it to at
>>> least double of desired arc size.
>>>
>>> --Artem
>>>        
>> I mentioned it briefly, but vm.kmem_size_max was left at the default for
>> amd64.  At 330GB it is way above and beyond what will ever be allocated to
>> ARC:
>> $ sysctl vm.kmem_size_max
>> vm.kmem_size_max: 329853485875
>>
>>
>>
>>      
>