kmem_map too small: 3832475648 total allocated

Scott Long scottl at
Thu Apr 29 16:56:35 UTC 2010

On Apr 29, 2010, at 9:44 AM, Tom Evans wrote:
> On Thu, Apr 29, 2010 at 3:53 PM, Ollivier Robert
> <roberto at> wrote:
>> According to James R. Van Artsdalen:
>>> system is a Core i7 975 (3.33 GHz x 4 cores 3x threads per core) with 12
>>> GB of RAM, a 2x2TB ZFS boot pool and a second (idle) pool of 16x2TB.
>>> panic: kmem_malloc(131072): kmem_map too small: 3832475648 total allocated
>> Apart from the fact that you must at least set vm.kmem_size to something like 2x your RAM, one rule of thumb I've seen discussed for ZFS is that you will need approximatively 1 GB of RAM per TB of data so you may be a bit short here to get optimal perfs.
> Citation needed? I have a file server running amd64 8-STABLE with 4GB
> of RAM, 6 x 1.5 TB drives in raidz, and have never had any problems
> with memory usage. Are you saying that after my next update, adding
> another 6 x 1.5 TB drives, it will start being flaky and/or panicing
> with kmem_map too small errors?

I'm sorry, but I find it absolutely absurd that any filesystem has to wire down 2GB of RAM, and that the solution to panics is buy more RAM.


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