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

[Steven Timm <timm@xxxxxxxx>]

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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