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LI81319: USERS WHO SET OMP_PLACES=CORES OR OMP_PLACES=THREADS CAN CAUSE IT TO ALLOCATE MORE CORES THAN AVALIABLE AND FAILS TO EXECUTE

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APAR status

  • Closed as program error.

Error description

  • if  1 or more  core on each socket has
been set aside for overhead and is not
available for allocation. As a result,
creating threads that are bound to
unavailable cores fails if OMP_PLACES=cores or
OMP_PLACES=threads is set

Local fix

  • Specify which cores to use in OMP_PLACES explicitly. Turning off
processor binding also avoids the problem but it may hurt the
performance.
Use the SMP runtime with the fix for this
problem.

Problem summary

  • USERS AFFECTED:
Users who set OMP_PLACES=cores or OMP_PLACES=threads on Summit

PROBLEM DESCRIPTION:
On some hardware it could be the case that, each compute node
has 2
sockets, each socket has 22 cores.
However, 1 core on each socket has been set aside for overhead
and is not
available for allocation. As a result, creating threads that are
bound to unavailable cores fails.

Problem conclusion

  • This issue has been fixed.

Temporary fix

  • 



Comments


    

  • 



APAR Information




    

  • APAR number
    LI81319
    • 

  • Reported component name
    XL C/C++ LINUX
    • 

  • Reported component ID
    5725C7310
    • 

  • Reported release
    G11
    • 

  • Status
    CLOSED  PER
    • 

  • PE
    NoPE
    • 

  • HIPER
    NoHIPER
    • 

  • Special Attention
    NoSpecatt / Xsystem
    • 

  • Submitted date
    2020-04-02
    • 

  • Closed date
    2020-06-22
    • 

  • Last modified date
    2020-06-22
    • 





    

  • APAR is sysrouted FROM one or more of the following:
    

    • 

  • APAR is sysrouted TO one or more of the following:
    

    • 



Fix information


    

  • Fixed component name
    XL C/C++ LINUX
    • 

  • Fixed component ID
    5725C7310
    • 



Applicable component levels


    








      
              
                            

              

              [{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSXVZZ","label":"XL C\/C++ for Linux"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"G11","Line of Business":{"code":"LOB57","label":"Power"}}]
              

                          

          
 
        

      

    

      

        

          

            
Document Information


            

            


                        

            Modified date:
            

            23 June 2020
            

            
                      

        


        

        


      

    

  



    

  

  
    
            

          
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