R815 + Xen + NUMA

G.Bakalarski at icm.edu.pl G.Bakalarski at icm.edu.pl
Tue Mar 6 06:42:38 CST 2012

Hi All,

Does Anybody successfully run linux kernel with NUMA flag ON under Xen on R815

We get strange results with different Debian Xen kernel (by default NUMA is
ON) on R815 server (4x Opteron 6174 with 192GB memory) - tested: squeeze
3.1, 3.2 (wheezy) . Without Xen numactl sees 8 nodes. Xen itself reports also
8 nodes, but numactl in dom0 or domU even with all memory availabe report 3 to
6 nodes ...
Moreover IO performance to internal Raid (PERC) virtual disk - in fact read
performance affected - behaves very odd (e.g. streaming read randomly changes
from about 16MBytes/s to 250MBytes/s.

On the other side SLES 11 SP2 Xen kernel has NUMA flags OFF.

On yet another side I've recently read article showing that NUMA maybe
important for R815 ...

Any suggestions ??

Best regards,


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