ZFS kmem_map too small.

[Dag-Erling Smørgrav]

Pawel Jakub Dawidek <pjd at FreeBSD.org> writes:
> We'are about to branch RELENG_7 and I'd like to start discussion with
> folks that experience 'kmem_map too small' panic with the latest HEAD.

I've been getting it recently (twice in the last ten days).  Intel E6600
with 4 GB RAM running an amd64 kernel from September 25.  After the
first panic, I increased kmem_size_max to 2G so that I now have:

des at ds4 ~% sysctl -h vm | grep kmem
vm.kmem_size_scale: 3
vm.kmem_size_max: 2,147,483,648
vm.kmem_size_min: 0
vm.kmem_size: 1,381,412,864

After the second panic, I set kmem_size_max to 4G and kmem_size to 2G in
loader.conf, but I haven't rebooted yet.

No backtraces because the watchdog kicked in and rebooted the machine.
I now have tace_on_panic=1 and debugger_on_panic=0, so next time I
should get at least a backtrace, and a dump if I'm lucky.

Both panics occurred during the nightly rsync of my imap spool from my
mail server to my file server, where it is kept in a compressed dataset
which I snapshot every day.  The spool currently contains about 1.5 M
files with an average size of slightly less than 8 kB.

DES
-- 
Dag-Erling Smørgrav - des at des.no