Xen users - Jun 2008 - Xen / NUMA problems

Hi folks,

we are using a Tyan TK8W 2885 Mainboard (latest BIOS) w/ 2 Dual Core Opteron
280EE and 8GB of RAM (4GB per Socket). Furthermore we run CentOS 5.1 w/ Xen
3.2.1.  (build from SRPM). We also tried 3.2.0.

I tried both, the CentOS 5.1 Xen Kernel as well as the latest RHEL 5.2 Kernel
but we do not get two NUMA domains as we (in my opinion) are supposed to.

Do we need to recompile anything? If so how? and/or is it possible to force a
NUMA mode?

Thanks a lot

Kai

# xm list
...
release                : 2.6.18-92.1.1.el5xen
machine                : x86_64
nr_cpus                : 4
nr_nodes               : 1
cores_per_socket       : 2
threads_per_core       : 1
total_memory           : 8063
free_memory            : 128
node_to_cpu            : node0:0-3
xen_major              : 3
xen_minor              : 2
xen_extra              : .1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
xen_scheduler          : credit
xen_pagesize           : 4096
xen_changeset          : unavailable
xend_config_format     : 4

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On Tue, Jun 24, 2008 at 9:03 AM, Kai Mosebach <xen@komadev.de>
wrote:
> Hi folks,
>
> we are using a Tyan TK8W 2885 Mainboard (latest BIOS) w/ 2 Dual Core
Opteron 280EE and 8GB of RAM (4GB per Socket). Furthermore we run CentOS 5.1 w/
Xen 3.2.1.  (build from SRPM). We also tried 3.2.0.
>
> I tried both, the CentOS 5.1 Xen Kernel as well as the latest RHEL 5.2
Kernel but we do not get two NUMA domains as we (in my opinion) are supposed to.
>
> Do we need to recompile anything? If so how? and/or is it possible to force
a NUMA mode?
First, does that board support NUMA?  I''m not familiar with it, so I
have no idea.

Second, you are using RHEL, yes?  By default RHEL does not enable NUMA
in Xen.  You have to explicitly enable it.  You can recompile Xen, but
honestly, it''s far easier to pass a parameter at boot time via grub.

on the kernel line in grub, be sure to add "numa=on" and then check
the Xen messages as the hypervisor boots.

You will not see any NUMA stuff in dom0, IIRC, as dom0 is just a
privileged paravirt guest.  All the NUMA stuff will appear in the
hypervisor messages.

Cheers
Jeff

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