JDK-6329603 : CMS: +CMSClassUnloadingEnabled and +CMSPermGenSweepingEnabled by default
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 6
  • Priority: P3
  • Status: Closed
  • Resolution: Won't Fix
  • OS: generic
  • CPU: generic
  • Submitted: 2005-09-27
  • Updated: 2014-09-02
  • Resolved: 2014-09-02
Related Reports
Relates :  
JDK-6543076 - CMS: Adaptive collection of perm gen
Relates :  
JDK-6541037 - Ability to unload classes upon an explicit concurrent gc request
Description
Customers who care to reduce pause times further would turn off
class unloading as needed, knowing the needs of their applications.

We need to do refworkload/alacrity measurements to understand and
document the performance impact if any from such a switch.
Comments
CMSClassUnloadingEnabled is already default, and there is no CMSPermGenSweepingEnabled switch any more after JDK8 perm gen changes.
02-09-2014
EVALUATION This will need more work, since enabling perm gen collection appears to adversely impact remark times by more than we had anticipated. That investigation is formally deferred to Dolphin.
27-10-2005
SUGGESTED FIX change the default setting of these two flags in glogals.hpp.
27-09-2005
EVALUATION Should do by b55 if possible.
27-09-2005