JDK-7027529 : CMS: retire CMSUseOldDefaults flag
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 7
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2011-03-15
  • Updated: 2011-05-25
  • Resolved: 2011-04-24
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JDK 7 Other
7Fixed hs21Fixed
Related Reports
Relates :  
The flag CMSUseOldDefaults was provided in JDK 6 FCS when there had been a bunch of
performance enhancing changes to the defualt settings for CMS vis-a-vis JDK 5.
The idea was that JDK 5 customers who were relying on the old defaults in JDK 5
would continue to get (roughly) the old behaviour if they used this flag when
they moved to JDK 6. In effect this was a jumbo flag that provided a bunch of
default settings. During the past few years we have not come across any customer
who needed to rely on that flag, and moreover the general experience has been
of improved CMS performance after changing these defaults to what they are today
in JDK 6.

In this CR, we are proposing to remove and retire the flag CMSUseOldDefaults.

This CR should be release-noted in JDK 7.

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-comp/hotspot/rev/dde920245681

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-rt/hotspot/rev/dde920245681

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/dde920245681

SUGGESTED FIX Remove the flag and the associated settings in JDK 7.

EVALUATION We are rolling this change with the changeset for:- 6896099 Integrate CMS heap ergo with default heap sizing ergo.