Setting "zfs_arc_max" value in FreeBSD 8.

[jhell]

On Wed, 20 Jan 2010 05:14, Alexander@ wrote:
> Quoting jhell <jhell at DataIX.net> (from Tue, 19 Jan 2010 09:45:58 -0500):
>
>> On 1/19/2010 5:16 AM, Sherin George wrote:
>>> Thanks Ivan :)
>>> 
>>> I found It. add following in /boot/loader.conf
>>> 
>>> ===================
>>> vfs.zfs.arc_max="10244M"
>>> ===================
>
>> I just thought I would give a shout at this for stable/7 as of last
>> week. I am not sure if this is just me but I had tried to adjust
>> zfs_arc_max and found out that it was unadjusted to my value after the
>> system came back up.
>> 
>> Anyone know if it is adjustable on a system with 1024MB of ram ? Is this
>> just being auto calculated by some other value ?
>
> Can you confirm that you made the modification in /boot/loader.conf, and that 
> you used the double-quotes around the value as shown above?
>
> The code in 7-stable regarding this is the same as in 8-stable and 9-current, 
> so if it is done correctly, it has to change accordingly.
>
> Bye,
> Alexander.
>
>

Yes,

The sysctl in question on my machine is/was put in loader.conf with the 
double quotes.

Every time I have set this before I was trying to set it to a value >= 
512M which with the values below must have not been excepted and fell back 
to 320M.

If I set this to a value of <= 511M it works fine which leads me to 
believe this is limited by some other value listed below ?

dmesg:
real memory  = 1072107520 (1022 MB)
avail memory = 1035038720 (987 MB)

loader.conf:
kern.maxusers="512"	<< Not sure if this has anything to do with it.
vfs.zfs.arc_min="80M"
vfs.zfs.arc_max="512M"	<< This fails. stays at 335544320.
vm.kmem_size="512M"
vm.kmem_size_max="512M"	<< Maybe this one.
kern.ipc.semmni="40"
kern.ipc.semmns="300"
kern.maxdsiz="536870912"
kern.maxfiles="16384"


There is points in time where I would like to dedicate 2/3 of ram or more 
using ZFS arc_max but somehow I feel like I have limited this by one of 
the other values that I had not had the time to look into if they impact 
larger values of arc_max being set.

Thank you,

Best regards,,

-- 

  jhell