Fresh 7.0 Install: Fatal Trap 12 panic when put under load

Jeremy Chadwick koitsu at
Thu Sep 11 09:20:49 UTC 2008

On Thu, Sep 11, 2008 at 10:38:36AM +0200, Michael Grant wrote:
> My box crashed again:
> panic: kmem_malloc(4096): kmem_map too small: 1073741824 total allocated
> cpuid = 0
> Uptime: 33d11h12m58s
> Dumping 3327 MB (2 chunks)
>   chunk 0: 1MB (151 pages) ... ok
>   chunk 1: 3327MB (851568 pages)  <---hung here
> Still no valid dump.
> There is 4gig of physical memory in the machine.
> In /boot/loader.conf, I currently have the following:
> vm.kmem_size=1G
> vm.kmem_size_max=1G
> vm.kmem_size_scale=2
> and in my kernel conf file I have:
> options         KVA_PAGES=512
> It stayed up for 33 days this time.  Is there anything else I can do?

First and foremost: are you using ZFS on this machine?  If so, there are
many tunables you can apply to try and limit this; I'm willing to bet
it's ARC which is doing it.  See below.

In general, it appears that you need to increase the maximum range of
kmem.  The kernel attempted to utilise more than 1GB, and your limit is
1G.  My machines running RELENG_7 on amd64, with only 2GB of RAM
installed, use the following tunables in loader.conf:


If ZFS is in use, I recommend these as well:


Do not increase kmem_size any larger than 1.5GB; the amount of RAM you
have in the machine, with regards to RELENG_7, will not help.  This is a
known limitation which has been fixed in HEAD/CURRENT (where the limit
has been increased to 512GB).  See the "Kernel" section below; you'll
see the applicable item.

Your only solution may be to run HEAD/CURRENT.

| Jeremy Chadwick                                jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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