IV57808: OBJECT HEAP MIGHT BE NOT ALLOCATED IN LARGE PAGES IF -XMX VALUE IS NOT ALIGNED TO PAGE SIZE

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  Object heap might be not allocated in Large Pages requested by
  -Xlp option if provided -Xmx value is not aligned to LP size.
  The taken physical page size can be checked in GC verbose
  log:This is example of aligned -Xmx value: 3G heap is requested
  and it is allocated in 1G LP:./java -Xlp -Xaggressive
  -Xcompressedrefs -Xmx3072m -verbose:gc -version 2>&1 <PIPE>
  egrep "RefsShift<PIPE>pageSize"<attribute
  name="compressedRefsShift" value="0x3" /><attribute
  name="pageSize" value="0x40000000" />This is example of not
  aligned -Xmx value. Memory is taken in 4K pages:./java -Xlp
  -Xaggressive -Xcompressedrefs -Xmx3071m -verbose:gc -version
  2>&1 <PIPE> egrep "RefsShift<PIPE>pageSize"<attribute
  name="compressedRefsShift" value="0x3" /><attribute
  name="pageSize" value="0x1000" />
  

Local fix

• Use -Xmx value aligned to requested LP sizeTo get information
  about available LP sizes use -verbose:sizes
  

Problem summary

• If Object Heap allocation is requested in Large Pages by using
  -Xlp option but provided -Xmx value is not aligned to desired LP
  size an allocation in LP can be refused and memory is taken in
  small pages.
  

Problem conclusion

• This APAR will be fixed in the following Java Releases:
     7 R1 SR1       (7.1.1.0)
  .
  Memory allocation request does rounding up for -Xmx value to
  desired LP size
  

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

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