HP OpenVMS Systems

Processor Scheduling and Affinity?

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The Question is:

 
I have a 6 processor VAX 7700 and I want to restrict a process to a specific
 cpu and have nothing else run on that cpu.  How is this accomplished?
 

The Answer is :

 
  The following applies to OpenVMS Alpha.
 
  It is often best not to do this, as dedicating applications to
  processors can often acomplish little more than a political
  victory -- more often than not, dedicating processes can reduce
  aggregate throughput, particularly when the specified resources
  are not available or when access to available additional system
  resources is possible but not use is not authorized -- in the
  former case, the job(s) will remain stalled, and in the latter
  case the resources will remain idle.  (Without this restriction,
  OpenVMS would reschedule all computable jobs onto the available
  processor resources.)
 
  That said, to keep a process locked on processor 5 (in a system
  where processors are assumed to be numbered 0 through 5), within
  the context of the process itself use;
 
  $ set process /affinity /permanent /set=5 /clear=(0,1,2,3,4)
 
  The /permanent qualifier is crucial for the setting to remain in effect
  across image rundown.  Although the /clear qualifier is optional, the
  OpenVMS Wizard typically recommends its use as the SET mask will
  otherwise accumulate.
 
  For example, to keep a process on processor 4, outside the context of the
  process use;
 
  $ set process /affinity /set=4 /clear=(0,1,2,3,5) /identification=PID
 
  where PID is the process identification of the target process.
 
  This command requires the ALTPRI privilege.  This command may also
  require the GROUP or WORLD privilege, depending on the UIC owner of
  the current process and the UIC owner of the target process.
 
  For those of you running on certain OpenVMS Alpha systems -- and
  those systems with NUMA support -- that are interested in this and
  similar process-scheduling topics, you will want to explore the DCL
  command:
 
    $ set process /rad
 
  Process affinity support is not available on OpenVMS VAX.
 

  

     

     
answer written or last revised on ( 2-APR-2003 )
     
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