[Xen-devel] Logical NUMA error during boot, and RFC patch

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Hello,

XenServer have recently acquired a quad-socket AMD Interlagos server and
I have been playing around with it, and discovered a logical error in
how Xen detects numa nodes.

The server has 8 NUMA nodes, 4 of which have memory attached (the even
nodes - see SRAT.dsl attached).  This means that that
node_set_online(nodeid) gets called for each node with memory attached. 
Later, in srat_detect_node(), node gets set to 0 if it was NUMA_NO_NODE,
or if not node_online().  This leads to all the processors on the odd
nodes being assigned to node 0, even though the odd nodes are present
(see interlagos-xl-info-n.log)

I present an RFC patch which changes srat_detect_node() to call
node_set_online() for each node, which appears to fix the logic.

Is this a sensible place to set the node online, or is there a better
way to fix this logic?

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com

Attachment: SRAT.dsl
Description: Text Data

Attachment: interlagos-xl-info-n.log
Description: Text Data

Attachment: RFC-fix-numa-online.patch
Description: Text Data

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