VM65189: EXCESSIVE SYSTEM OVERHEAD FOR PGMBK STORAGE RECLAIM

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• As a system becomes more storage constrained, users may
  experience noticeable delays because of SYSTEMMP work performing
   PGMBK reclaim.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: ALL USERS OF z/VM                            *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  A severe system slowdown occurred because processing of the DPPL
  (Deferred PGMBK Paging List) is continually re-invoking itself
  but accomplishing nothing.  Most of the PGMBKs on the DPPL
  belonged to one or two dominant users, and DPPL processing was
  unable to remove PGMBKs from the list because it could not
  obtain the need serializations to do so.  This is because the
  one or two dominant users were almost always dispatched and
  running.  DPPL processing was trying to run because there was a
  need (the below 2G contigs list was 1 below low threshhold) and
  the DPPL wasn't empty.  Because of this situation, DPPL
  processing would restack itself to run immediately when it
  finished.  This continual running of DPPL processing was
  actually preventing the one or two dominant users from finishing
  their runs and releasing the serializations that DPPL processing
  needed.
  

Problem conclusion

• HCPALRPP logic was changed so that stacking itself also opened a
  window of time to allow other things to run.  This time delay
  window will be based on the length of time DPPL processing took
  and whether or not DPPL processing was fruitful, or whether an
  emergency condition still exists.  More monitor fields were also
  added for RAS.
  

Temporary fix

• FOR RELEASE VM/ESA CP/ESA R630 :
  PREREQ: VM65352 VM64770
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

• ×**** PE16/04/12 FIX IN ERROR. SEE APAR VM65820  FOR DESCRIPTION
  

APAR Information

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

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

  UM34657

Modules/Macros

• HCPALR   HCPHRU   HCPMOT   HCPRSMBK MRSTORSG
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R630 PSY UM34657

     UP16/03/23 P 1602 ¢

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.