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RE: [Xen-users] Attempt to allocate order 5 skbuff. Increase MAX_SKBUFF_ORDER



Both of these domU's are back up now in a different configuration
which does not use NAT and does not have the iptable_nat module
loaded, and things are looking much better.  So far we have
not seen the MAX_SKBUFF_ORDER problem at all.  We will
continue to monitor.

Thanks for your help.

Steve Timm





On Wed, 6 May 2009, Fischer, Anna wrote:

Subject: RE: [Xen-users] Attempt to allocate order 5 skbuff. Increase
MAX_SKBUFF_ORDER

Well if you don't need it then just try and remove the NAT module
using "modprobe -r iptable_nat". And see if that makes any
difference.


Can't remove it, get the message
"module is in use".. not sure by what.

Do you have any rules in the NAT table? E.g. check "iptables -t nat -
L". Then remove those rules and try removing the module again. I doubt
that the NAT module is the core of your problem though.

Yes it turns out we did.  This server is an LVS "real server" back
end and Horm's transparent proxy is in use.  that's
what the NAT is being used for.


CONFIG_XEN_SKBUFF is on in my config.
There is no MAX_SKBUFF_ORDER parameter anywhere in my source tree,
much less the config file.

MAX_SKBUFF_ORDER is not a configuration option. It is part of the
Dom0/DomU kernel code.

I have grepped the whole kernel code from the kernel which I'm
running, which is unmodified from the redhat SRPMS as delivered with
version 5, update 3. 2.6.18-128.1.6.el5xen.  I don't find
the string MAX_SKBUFF_ORDER anywhere in there.  Which source file
should
it be in?



Your posted kernel config is from your Dom0? You said before that you
are running a 64-bit Dom0. You need to check the CONFIG_XEN_SKBUFF
option in the Dom0 config. I am in general wondering if you might have
issues with your DomU/Dom0 configuration. How did you install those
kernels? Did you install them using the distro? Did you compile them
yourself? I assume you also run a 64-bit hypervisor?

Yes running 64-bit dom0 and hypervisor.  the kernel config
is actually the same for both dom0 and domU as in redhattish xen
you actually run the same kernel-xen in both.  Only difference is
that it is 64-bit for the dom0 and 32-bit for the domU.

How can you have the same kernel configuration for a 32-bit and a 64-bit system 
? Have you edited those yourself and then compiled the kernels ? There are a 
lot of dependencies around the CONFIG_X86_64, CONFIG_X86_32 etc defines.


--
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
timm@xxxxxxxx  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.

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