VM65586: SIMULTANEOUS MULTITHREADING (SMT) AND CPU SCALABILITY

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Simultaneous multithreading (SMT) and increased CPU scalability
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Installations running z/VM on an IBM z13     *
  *                 that want to utilize Simultaneous            *
  *                 Multithreading (SMT) support for IFL         *
  *                 processors (which supports up to 32 logical  *
  *                 cores) or to utilize up to 64 logical        *
  *                 single threaded cores.                       *
  ****************************************************************
  * PROBLEM DESCRIPTION: SMT and up to 64 core support           *
  *                      required in z/VM for IBM z13 (z13)      *
  *                      D/T2964.                                *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  SMT and up to 64 core support required in z/VM for IBM z13
  (z13) D/T2964.
  

Problem conclusion

Temporary fix

Comments

• With the PTF for APAR VM65586, z/VM provides host exploitation
  support for the simultaneous multithreading (SMT) facility on
  the IBM z13, which will enable z/VM to dispatch work on up to
  two threads (logical CPUs) of an IFL processor core. z/VM
  multithreading support is enabled only for IFL processors in a
  LINUX only mode or z/VM mode logical partition.  This may
  result in increased work throughput per core from more
  efficient use of shared core resources.
  Additionally, z/VM will now support up to 64 logical processors
  on the IBM z13:
  - 64 cores with multithreading disabled
  - 32 cores (up to 2 threads per core) with multithreading
     enabled.
  z/VM continues to support up to 32 logical processors on
  prior machines.
  
  SMT support is available on a z/VM system only if the facility
  is installed on the hardware and enabled on the z/VM system
  with the MULTITHREADING system configuration statement. The
  MULTITHREADING statement is optional, and multithreading is
  disabled if the statement is omitted.  z/VM enablement of
  multithreading requires that z/VM is configured to run with
  the HiperDispatch vertical polarization mode enabled and with
  the dispatcher work distribution mode set for reshuffle. If
  the system configuration file changes either of these
  conditions so they are not set correctly for multithreading,
  the system will come up with multithreading disabled. SMT
  cannot be enabled or disabled without changing the system
  configuration file and issuing a re-IPL. The new QUERY
  MULTITHREAD (MT) command can be used to discover if
  SMT is enabled on a system.
  
  z/VM host support for SMT does not virtualize threads for
  guest exploitation.
  
  Performance Toolkit support for SMT requires APAR VM65529.
  Stand-alone dump support for SMT requires APARs VM65676 and
  VM65677.
  
  To support this APAR, new editions of the following publications
  are available:
     * z/VM V6.3 CP Commands and Utilities Reference, SC24-6175-06
        Information on new commands (INDICATE MT, QUERY MT,
        VARY CORE) and changed commands
     * z/VM V6.3 CP Messages and Codes, GC24-6177-06
        Information on new messages and Abend codes
     * z/VM V6.3 CP Planning and Administration, SC24-6178-07
        Information on the new MULTITHREADING statement,
        changed SRM statement, new accounting record
        (type F), and changed accounting records
     * z/VM V6.3 CP Programming Services, SC24-6179-06
        Information on new programming interfaces
     * z/VM V6.3 Diagnosis Guide, GC24-6187-04
        Information on new trace codes
     * z/VM V6.3 General Information, GC24-6193-08
     * z/VM V6.3 License Information, GC24-6200-10
     * z/VM V6.3 Migration Guide, GC24-6201-06
        Information on the new monitor record,  Domain 5
        Record 20, and several changed monitor records
     * z/VM V6.3 Performance, SC24-6208-06
        Information on the new monitor record
  
  For more information about the publication changes,
  refer to the Summary of Changes section located near
  the beginning of each publication.
  .
  See http://www.vm.ibm.com/library/ for the online version
  of the updated publications.
  .
  
  Note: z/VM CPU pools provide a mechanism for limiting the CPU
  resources consumed by a group of virtual machines to a specific
  capacity. In an environment without SMT, these capacities are
  enforced in terms of a number of cores. In an SMT environment,
  these capacities are enforced in terms of a number of threads.
  Consequently, it might be necessary to increase the capacities
  of CPU pools, in order to provide adequate resource to CPU
  pool members.
  
  Note:  If you are using a VM mode partition with multithreaded
  logical IFLs then, in order for z/VM to use these IFLs, guests
  need to have virtual IFLs defined.  For information on how to
  define virtual IFLs, see Running Guest Operating Systems,
  Chapter 1 - "Fundamentals of Guest Support in z/VM", section
  "Specialty Engine Support".
  

APAR Information

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

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

  UM34551 UM34552

Modules/Macros

• CADE     CADGE    CADGNE   CADNE    CBITABLE
  CPLOAD   CPQUERY  CPSYNTAX CPTRACE  CPUUSE   HCPACC   HCPACL
  
  ***This field was truncated.  To obtain the full apar record, please contact your local support center.***
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• RA63 PSY UM34551

     UP15/09/22 P 1502

• R630 PSY UM34552

     UP15/03/12 P 1502

Fix is available

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