Overview:

• Using placement sets it is created a pool of nodes with unset resource. When scheduler tries to run a job, it considers to fit a job into this pool. The value of unset resource is "\"\"". A new parameter allows to control whether or not this pool is created.

Interface 1: only_explicit_psets

• Visibility: Public
• Change Control: stable
• Synopsis: scheduler attribute; attribute can control creation of pool of nodes with unset resource in placement sets
• Details: Scheduler attribute. Specifies whether or not the scheduler creates a pool of nodes with unset resource in placement sets. Default value is False. 
  • Set to False means: The behavior is unchanged. The pool with unset resource is created. If you use placement sets, scheduler creates pools of nodes: one pool per value and one pool for nodes with unset value. The scheduler tries to fit a job into the pools from the smallest one to the largest one. 
  • Set to True means: The pool with unset resource is NOT created and the nodes with unset resources are skipped in this placement set.
• Example:
  • create resource infiniband
    set resource infiniband type = string
    set resource infiniband flag = h
    ...
    set node n1 infiniband = A
    set node n2 infiniband = B
    unset node n3 infiniband
    
    set sched do_not_span_psets = True
    set sched only_explicit_psets = True
    
    $ qsub -l place=group=infiniband
    The job can run on n1 or n2 but will never run on n3 with 'only_explicit_psets = True'.

Draft of Placement Sets documentation

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