FreeBSD 7.2-RC1 - ZFS related kernel panic "kmem_map too small"
gary.jennejohn at freenet.de
Wed Apr 22 10:30:23 UTC 2009
On Wed, 22 Apr 2009 00:34:00 +0200
Kai Gallasch <gallasch at free.de> wrote:
[snip a lot of stuff]
> In /usr/src/UPDATING I read:
> ZFS users on amd64 machines with 4GB or more of RAM should
> reevaluate their need for setting vm.kmem_size_max and
> vm.kmem_size manually. In fact, after recent changes to the
> kernel, the default value of vm.kmem_size is larger than the
> suggested manual setting in most ZFS/FreeBSD tuning guides.
> So I understood this as "vm.kmem_size is set unnecessary large by
> default. You should think about decreasing it to save some RAM"
> On my amd64 server the default values of kmem_size are
> vm.kmem_size_scale: 3
> vm.kmem_size_max: 3865468109
> vm.kmem_size_min: 0
> vm.kmem_size: 1201446912
> Can someone give me a hint how to debug this problem further, or how to
> find some reasonable values for setting vm.kmem_size_max and
> vm.kmem_size with 16G of RAM?
Hmm, I wonder whether this applies to 7.2-RC1. I don't know whether
the kernel changes have been committed to 7.2 or whether they were
already present when we started work on 7.2 because I haven't been
paying much attention.
On my 8-current amd64 machine with only 4GB of RAM I see larger values
than you see with 16GB:
More information about the freebsd-fs