On 8/17/12 7:15 AM, Marie Bacuno II wrote:
On Aug 16, 2012, at 18:47, Garrett Cooper <yaneg...@gmail.com> wrote:
On Thu, Aug 16, 2012 at 6:44 PM, Garrett Cooper <yaneg...@gmail.com> wrote:
On Thu, Aug 16, 2012 at 5:46 PM, Gezeala M. Bacuño II <geze...@gmail.com> 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`.
Also, it's a tunable, not a sysctl... so you need to set the value in
/boot/loader.conf .
-Garrett
Thanks for the quick reply.
Yes, had it set on /boot/loader.conf and by trial and error on the loader
prompt.
We were able to bump it to 400G successfully. Tried 500G and 450G and the
machine just spews out garbage in the screen.
The latest output from "zfs-stats -a" with vm.kmem_size_max="400G" is in the
forum: http://forums.freebsd.org/showthread.php?t=33977
About the code, I am looking into amd64 arch. Still checking the values of the
variables.. Can't just retrieve them using getconf. If you can point me to a
doxygen like documentation appreciate it a lot.
Where does the constant value 329853485875 came from?
It comes from this macro:
#define VM_KMEM_SIZE_MAX ((VM_MAX_KERNEL_ADDRESS - \
VM_MIN_KERNEL_ADDRESS + 1) * 3 / 5)
((1<<39) * 3 / 5) = 329853488332
AFAIK, VM_MAX_KERNEL_ADDRESS is limited to 512Gb. May be it's time to
increase it again. I would asked kib@ or alc@ about that.
--
Andrey Zonov
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