ZFS kmem_map too small.

[Claus Guttesen]

> 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'm trying hard to reproduce it and I can't, so I need to gather more
> info how you are able to provoke this panic.
>
> What I did was to rsync 200 FreeBSD src trees from one directory to
> another on the same ZFS file system. It worked fine.

I have a server which gets these 'kmem_map too small' stops. I have an
Dell PE2850 and is running current as of Sept. 26'th 2007. The error
is easy to trigger. I have copied 90 GB of jpeg-files with a size of
approx. 1 MB and a thumbnail at 4 KB. These files are distributed in
approx. 700 folders. The files resides on it's own partition.

It crashed while I copied the files down to the server and the server
crashed copying the files on to another partiton on the same server.

Everytime it crashed with a 'kmem_map too small' it seemed to want
slightly more than was set aside in vm.kmem_size. So I adjusted it
upwards from 512M, 640M and finally 768M.

vm.kmem_size_max was set at 512M, 640M and finally 1024M (1 GB). It
crashed with alot of file i/o. When I stopped copying files the server
has been stable.

It did *not* occur with a kernel build at May 25'th 2007. So now I
will either downgrade or move the zfs-partitions to (open)solaris. We
are getting closer to our xmas-season and I need to have a rock-solid
zfs-server.

-- 
regards
Claus

When lenity and cruelty play for a kingdom,
the gentlest gamester is the soonest winner.

Shakespeare