IV96569: EXTRA 2GB PAGE ALLOCATED FOR THE OBJECT HEAP ON Z/OS OR ZLINUX

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  The JVM allocates more memory for the object heap than expected.
  For example, a JVM launched with options "-Xnocompressedrefs
  -Xmx15360M-Xlp:objectheap:pagesize=2G,nonpageable"
  allocates a 18G heap. Shown in a javacore as follows:
  "+--Java Heap: 19,327,352,832 bytes / 1 allocation"
  

Local fix

• Do not use 2GB large pages
  

Problem summary

• It is normal behavior for the allocated size of the object heap
  to be rounded up to the physical page size. For example, an
  object heap allocation size of 15GB in 2GB pages is rounded to
  16GB. When running the -Xnocompressedrefs JVM (either explicitly
  or when the object heap size is larger than supported by the
  compressedrefs JVM), regardless of the page size an extra page
  is added to the object heap size on z/OS and zLinux for
  performance reasons. On z/OS an extra 4/8 bytes are required for
  31-bit/64-bit JVMs which may use an entire extra page of memory.
  

Problem conclusion

• An extra page is only added to the object heap size when the
  page size is smaller than 1GB. No extra bytes are required on
  z/OS.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR5       (8.0.5.0)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• 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

  J9 COMMON CODE

• Fixed component ID

  620700127

Applicable component levels

• R270 PSY

     UP