vm.kmem_size settings doesn't affect loader?

Alexandre "Sunny" Kovalenko gaijin.k at gmail.com
Thu Sep 25 15:47:10 UTC 2008

On Thu, 2008-09-25 at 16:10 +0100, Pete French wrote:
> > These are the tuning settings I use:
> >
> > vm.kmem_size="1536M"
> > vm.kmem_size_max="1536M"
> > vfs.zfs.arc_min="16M"
> > vfs.zfs.arc_max="64M"
> >
> > The entire copying process took almost 2 hours.  Not once did I
> > experience kmem exhaustion.  I can *guarantee* that I would have crashed
> > the box numerous times had I not tuned the machine with the values
> > above.
> I am interested in the last two values you have there - I also use ZFS and
> tune to prevent memory exhaustion. I tune kmem_size, but I have not bothered
> toi set the arc_min - and the default appears to be 16M anyway. The arc_max
> value I do set, but I got dreadful performance when I had it at 6M, so
> I upped it to 128M. This has not resulted in any panics, and gives much better
> performance. As I understand it there is only one ARC, and it comes from
> kernel space too, so setting it to an extra 64 meg should not use that much
> more memory, yes ?
On my RELENG_7 (circa August 14th) 

vfs.zfs.arc_min: 16777216
vfs.zfs.arc_max: 402653184

seem to be set by default. Yes, that is "384M".

I have 


set in my /boot/loader.conf, and


set in /etc/sysctl.conf

This is amd64 with 3GB of real memory. ZFS pool is used to serve music,
digital pictures and video to the rest of household, as well as provide
target for the weekly backups from couple of Windows desktops, so use is
not that heavy. Machine has been up for 22 days and has shown no ill
effects that I can notice.

Alexandre "Sunny" Kovalenko (Олександр Коваленко)

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