Forum discussion (EDD review).

Overview:

In order to support Cray features like requesting particular NUMA nodes, or some number of NUMA nodes, PBS had created one vnode for each NUMA node.
Sites have requested the ability to change the way PBS reports the Cray nodes, so that they can have fewer vnodes to deal with and not
encounter some of the differences that multiple vnodes per host brings.

The default behavior of PBS will be changed to create a vnode per compute node by default.
 

New Interface: vnode_per_numa_node

• Visibility: PBS Private
• Change Control: Experimental
• Details:
  • New interface: new mom_priv/config variable.
  • vnode_per_numa_node is a Boolean. 
    Setting it to FALSE will cause PBS to create one vnode per Cray compute node.  This is the default behavior
    when $vnode_per_numa_node is not set in mom_priv/config.
    Setting it to TRUE will cause PBS to create one vnode per Cray numa node.
  • the value of vnode_per_numa_node should be set to the same value on all of the PBS moms for that Cray system.
    
    

Interface: PBScrayseg

• resources_available.PBScrayseg will be set to 0 when vnode_per_numa_node is unset or set to FALSE
• resources_available.PBScrayseg will be set to the segment ordinal of the associated NUMA node when vnode_per_numa_node is set to TRUE

Administrator's instructions.

• When changing from one version of PBS using one type of vnode create versus another, you must first:
  
  • Quiesce the system (ensure there are no running jobs).
  • Remove all existing vnodes of the vntype cray_compute. The easiest way to do this is to delete all vnodes using 
    • qmgr -c "delete node @default"
  • Stop the version of the mom that create vnodes per NUMA node
  • Start the new version of MoM that will create vnodes per compute node
  • All moms on a Cray X* system must be of the same PBS version.
  • On the server add the MoMs back using qmgr: qmgr -c "create node <mom name>"

Definition of technical terms, spelling out acronyms and abbreviations.