JDK-6896084 : VM does not reserve protected page below heap for compressed oops implicit null checks
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: hs17
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • OS: solaris
  • CPU: x86
  • Submitted: 2009-10-28
  • Updated: 2010-04-03
  • Resolved: 2010-01-14
The Version table provides details related to the release that this issue/RFE will be addressed.

Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

To download the current JDK release, click here.
JDK 6 JDK 7 Other
6u18Fixed 7Fixed hs16Fixed
Related Reports
Relates :  
JDK-6716785 - implicit null checks not triggering with CompressedOops
Description
VM should reserve protected page below heap for compressed oops implicit null checks if zero base can not be used.
But the changes for 6791178: "zero based compressed oops " change code in such way that the page is not reserver
which could again cause 6716785: "implicit null checks not triggering with CompressedOops" problem.
Comments
EVALUATION http://hg.openjdk.java.net/hsx/hsx16/master/rev/248f0ad25d21
13-11-2009
EVALUATION http://hg.openjdk.java.net/hsx/hsx16/baseline/rev/248f0ad25d21
06-11-2009
PUBLIC COMMENTS Problem: VM should reserve protected page below heap for compressed oops implicit null checks in compiled code (see 6716785). After zero based compressed oops changes (6791178) the page is not reserved because undefined narrow_oop_base (NULL by default) is used in ReservedHeapSpace() to determine if the page is needed. Solution: Set narrow_oop_base and narrow_oop_use_implicit_null_checks values according to compressed oops encoding mode in Universe::preferred_heap_base() which is called before ReservedHeapSpace() constructors.
03-11-2009
EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-comp/hotspot/rev/f334aec453a1
30-10-2009
EVALUATION Still undefined Universe::narrow_oop_base() is used in ReservedHeapSpace() to determine if the protected page is needed.
28-10-2009