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VM65988: NEW FUNCTION : PROCESSOR SCALABILITY EFFICIENCY IMPROVEMENTS SHARED-EXCLUSIVE SPINLOCK IMPROVEMENTS

A fix is available

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You can track all active APARs for this component.

APAR status

  • Closed as new function.

Error description

  • z/VM spinlock performance improvements
    

Local fix

  • N/A
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: Systems experiencing more than 10% system    *
    *                 overhead with indications of high spinlock   *
    *                 overhead for SRMSLOCK, HCPTRQLK, or DSVLOCK. *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    ****************************************************************
    * RECOMMENDATION: APPLY PTF                                    *
    ****************************************************************
    This APAR provides improvements to reduce system overhead
    from the Scheduler Lock (SRMSLOCK), TRQBK Queue Lock
    (HCPTRQLK),and Dispatch Vector Lock (DSVLOCK).
    
    Systems experiencing more than 10% system overhead with
    indications that SRMSLOCK, HCPTRQLK or DSVLOCK spinlock
    contention are a significant factor. This contention is
    observed as high levels of spin time on these locks, or
    high rates of DIAG x'9C' issued from HCPDSP.
    
    Perfkit LOCKACT report FCX326 and Monitor record D0R23
    MRSYTLCK provides information on spinlocks including SRMSLOCK,
    HCPTRQKLK and DSVLOCK.
    
    Perfkit PROCSUM report FCX239 and Monitor record D0R13
    MRSYTSCP provides information on the rate of Diagnose 9C
    issued by HCPDSP.
    

Problem conclusion

Temporary fix

  • FOR RELEASE VM/ESA CP/ESA R640 :
    PREREQ: VM65943 VM65942
    CO-REQ: NONE
    IF-REQ: NONE
    

Comments

  • With the PTF for APAR VM65988, the z/VM hypervisor has been
    enhanced to manage its spinlocks more efficiently and thereby
    reduce system overhead.  This enhancement will contribute to
    improved performance and throughput and thereby help to improve
    overall system capacity by allowing additional work to be
    performed.  While most workload configurations could benefit to
    some extent, the improvements are greatest for workloads using
    a larger number of logical CPUs.
    
    The shared-exclusive spinlock manager was redesigned to use
    more cache-efficient data structures and algorithms which
    reduce the likelihood of lock contention for the Scheduler
    Lock (SRMSLOCK) and Topology Lock (HCPDSVTL). This new spinlock
    design is not dependent on new processor architecture.
    
    A new Monitor sample record D5R22 MRPRCSXL "Shared-Exclusive
    Spinlock Utilization" was added to provide a more detailed
    reporting of the usage of the new shared-exclusive spinlocks
    on a per-processor basis. However, the new shared-exclusive
    spinlock manager statistics are reported in the existing
    Monitor D0R23 MRSYTLCK record in a compatible manner.
    
    The time spent spinning in HCPDSP's internal spin loop used
    to acquire a share of the Scheduler Lock was previously
    unreported as spinlock spin time.  It is now included in
    SRMSLOCK reporting in Monitor D0R23 MRSYTLCK, SYTPRP_PFXSPINT
    in Monitor D0R2 MRSYTPRP, as well as the new D5R22 MRPRCSXL
    sample record.
    
    This internal spinloop in HCPDSP was made more efficient as
    part of the shared-exclusive spinlock manager redesign.  In
    partitions with shared processors the only external indicator
    of SRMSLOCK contention in HCPDSP was the Diagnose 9C rate
    issued from HCPDSP as reported in Perfkit PROCSUM report
    FCX239 and Monitor record D0R13 MRSYTSCP.  With this
    improvement the reported SRMSLOCK spin time may increase
    somewhat, but time spent in HCPDSP should be reduced.  Reduced
    time in HCPDSP should result in lower System time.  A
    reduction in the Diagnose 9C rate from HCPDSP is expected.
    
    The HCPTRQLK and DSVLOCK exclusive-only spinlock algorithms
    have been adjusted to operate best on D/T3906 and D/T3907
    hardware without causing degradation when running on older
    models.
    
    The support is available on all hardware supported by z/VM
    V6.4, including D/T3906 LinuxONE Emperor II and IBM z14.
    However, the improvements for HCPTRQLK and DSVLOCK depend on
    efficiencies unique to the LinuxONE Emperor II and z14.
    
    The following publications have been updated:
    
     - GC24-6177-10, z/VM: CP Messages and Codes
     - SC24-6208-09, z/VM: Performance
     - GC24-6201-12, z/VM: Migration Guide
     - GC24-6187-07, z/VM: Diagnosis Guide
     - SC24-6175-11, z/VM: CP Commands and Utilities Reference
    

APAR Information

  • APAR number

    VM65988

  • Reported component name

    VM CP

  • Reported component ID

    568411202

  • Reported release

    640

  • Status

    CLOSED UR1

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    YesSpecatt / New Function / Xsystem

  • Submitted date

    2017-02-06

  • Closed date

    2017-08-23

  • Last modified date

    2019-10-18

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

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

    UM35214

Modules/Macros

  • CBITABLE CPLOAD   HCPAEP   HCPAFF   HCPAFR   HCPAFS   HCPALD
    HCPALF   HCPALG   HCPALL   HCPALR   HCPALU   HCPAMD   HCPAMI
    HCPAMP   HCPAMR   HCPAPI   HCPAPJ   HCPASERT HCPASR   HCPASRBK
    HCPBMS   HCPBUT   HCPBVM   HCPCBI   HCPCCF   HCPCFM   HCPCORBK
    HCPCPA   HCPCPU   HCPCRS   HCPCSA   HCPCUP   HCPCVT   HCPDSB
    HCPDSP   HCPDSV   HCPDSVBK HCPEQUAT HCPFRD   HCPFRE   HCPFRF
    HCPGRB   HCPHAS   HCPHAT   HCPHIC   HCPHIP   HCPHIP$  HCPHIS
    HCPHPC   HCPHRU   HCPHTF   HCPHVR   HCPICU   HCPIOJ   HCPISM
    HCPISR   HCPIST   HCPKCL   HCPKCT   HCPKCW   HCPLAN   HCPLGN
    HCPLKCOR HCPLKPLD HCPLKSCH HCPLKTOP HCPLKTRQ HCPLMC   HCPLOC
    HCPLOCBK HCPMCI   HCPMCS   HCPMCW   HCPMDLAT HCPMNP   HCPMNU
    HCPMOL   HCPMOM   HCPMONEQ HCPMOP   HCPMOT   HCPMPC   HCPMPF
    HCPMPS   HCPMSM   HCPMTC   HCPMTF   HCPMTO   HCPMTS   HCPNDM
    HCPNOO   HCPNSC   HCPNSR   HCPOBTN  HCPOM1   HCPOM2   HCPPAF
    HCPPAH   HCPPAI   HCPPFE   HCPPFR   HCPPFX   HCPPFXPG HCPPGC
    HCPPGT   HCPPGU   HCPPLP   HCPPLSBK HCPPOD   HCPPOOLS HCPPPGMS
    HCPPPI   HCPPPR   HCPPTA   HCPPTC   HCPPTE   HCPPTF   HCPPTG
    HCPPTM   HCPQDO   HCPQFL   HCPQPT   HCPQSX   HCPRCC   HCPRCCBK
    HCPRDA   HCPRDD   HCPRFI   HCPRLB   HCPRLG   HCPRLI   HCPRLSE
    HCPRLU   HCPRP    HCPRSM   HCPSAM   HCPSCI   HCPSCJ   HCPSGP
    HCPSHI   HCPSMO   HCPSNR   HCPSPC   HCPSRM   HCPSRMBK HCPSRN
    HCPSSI   HCPSTK   HCPSTL   HCPSTM   HCPSTP   HCPSTQ   HCPSUBBK
    HCPSVC   HCPSVD   HCPSVU   HCPSXA   HCPSXL   HCPSXLBK HCPSXLLK
    HCPSXLUL HCPSXP   HCPSXU   HCPSYN   HCPSYN$  HCPSYNBK HCPSYNC
    HCPSZD   HCPSZE   HCPSZK   HCPSZL   HCPTDK   HCPTHQ   HCPTMF
    HCPTRQ   HCPTTA   HCPTTABK HCPTZN   HCPUDR   HCPULCOR HCPULPLD
    HCPULSCH HCPULTOP HCPULTRQ HCPUSYNC HCPVFM   HCPWAI   HCPXCM
    HCPXHC   HCPXHD   HCPXHE   HCPXRC   HCPXRP   HCPXTM   HCPXTR
    HCPZPC   HCPZPQ   HCWAI8   HCWA12   MRPRCSXL MRSYTLCK MRSYTPRP
    MRSYTSCG MRSYTSCP SUBBKS
    

Publications Referenced
GC24617710 SC24620809 GC24620112 GC24618707 SC24617511

Fix information

  • Fixed component name

    VM CP

  • Fixed component ID

    568411202

Applicable component levels

  • R640 PSY UM35214

       UP17/08/30 P 1802  

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.



Document information

More support for: z/VM family

Software version: 640

Operating system(s): z/VM

Reference #: VM65988

Modified date: 18 October 2019