Re: vm.kmem_size_max and vm.kmem_size capped at 329853485875 (~307GB)

On Thu, Aug 16, 2012 at 5:46 PM, Gezeala M. Bacuño II <[email protected]> wrote:
> Hello fellow listers,
>
> On a server with 512GB RAM it appears that vm.kmem_size_max is not
> being auto-tuned to use >329853485875 (~307GB).
>
> On this machine vm.kmem_size is equal to vm.kmem_size_max
>
> # from sysctl
> vm.kmem_size_max: 329853485875
> vm.kmem_size: 329853485875
>
> On a machine with 1GB of RAM, I have successfully set vm.kmem_size_max
> to 330GB and vm.kmem_size automatically adjusts to 1GB even if I
> manually set it in /boot/loader.conf.
>
> But on the machine with 512GB of RAM it just resets. For the machine
> to boot, we need to go to the loader prompt and issue:
>
> OK set vm.kmem_size_max="300G"
> OK boot
>
> On all PCBSD (8,9) or FreeBSD (8.1,8.2,9) machines we have,
> vm.kmem_size_max is always set to 329853485875.
>
> How can I increase vm.kmem_size_max to use at least 500GB? And how is
> 329853485875 determined (formula)? I need to increase vm.kmem_size_max
> and vm.kmem_size so I can set vfs.zfs.arc_max (ZFS ARC) to use say
> 490GB.
>
> I'm browsing thru the source code at
> http://fxr.watson.org/fxr/search?v=FREEBSD9&string=vm.kmem_size_max
> and I'm still trying to make sense of how vm.kmem_size_max is
> computed.
>
> I have posted the same topic on forums.freebsd.org but I'm not getting
> any recommendations.
>
> Please see the link for additional details:
> http://forums.freebsd.org/showthread.php?t=33977

Have you tried defining VM_KMEM_SIZE_MAX to your target value?

Its architecture specific BTW... see
sys/<architecture>/include/vmparam.h -- look for `VM_KMEM_SIZE_MAX`.

Cheers,
-Garrett
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