IJ33234: SEGMENTATION FAULT OR MISALIGNED OBJECT ERROR WITH HEAP SIZE GREATER THAN 25GB

APAR status

• Closed as program error.

Error description

• Error Message: A segmentation fault or misaligned object error
  might result after allocating a multidimensional array whose
  second dimension is zero.
  .
  Stack Trace: N/A
  .
  

Local fix

• Run the Java program with a maximum heap size of 25GB or less,
  or with the -Xnocompressedrefs option.  Some applications cannot
  be run with a smaller maximum heap size.  The -Xnocompressedrefs
  option might have an effect on program performance.
  

Problem summary

• When running with larger heap sizes, the Java Virtual Machine
  will compress addresses of Java objects and arrays.  This
  address compression imposes restrictions on alignment of those
  Java objects on particular byte boundaries.  Code generated by
  the just-in-time (JIT) compiler was allocating multidimensional
  arrays whose second dimension is zero in a way that caused each
  subarray and subsequently allocated objects to be allocated on
  an eight byte boundary.  However, with a heap size greater than
  25GB, with the -Xcompressedrefs option (which is the default),
  objects need to be allocated on a sixteen byte boundary.  This
  resulted in misaligned object errors or segmentation faults when
  the address of such a misaligned subarray or object was
  decompressed and dereferenced, or during garbage collection.
  

Problem conclusion

• The problem was corrected by ensuring that the code generated by
  the JIT compiler always allocates subarrays of multidimensional
  arrays with the required memory alignment.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR6 FP35  (8.0.6.35)
  .
  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

  JIT

• Fixed component ID

  620700124

Applicable component levels