JDK-6858496 : Clear all SoftReferences before reaching the GC overhead limit.
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 7
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2009-07-08
  • Updated: 2011-03-08
  • Resolved: 2011-03-08
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JDK 6 JDK 7 Other
6u21pFixed 7Fixed hs18Fixed
Related Reports
Relates :  
JDK-6980039 - Refs are not cleared when they should be
Relates :  
JDK-6976528 - PS: assert(!limit_exceeded || softrefs_clear) failed: Should have been cleared
Description
Before throwing an out-of-memory due to exceeding the GC overhead limit, try
a last-ditch GC to clear all the SoftReferences.
Comments
EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/0bfd3fb24150
14-04-2010
EVALUATION Clear all SoftReferences before throwing an out-of-memory due to GC overhead considerations.
13-08-2009
PUBLIC COMMENTS I'm adding here a small application, given to me by a customer, that aggressively touches all soft references and can cause an OOM in the server VM due to reaching the GC overhead limit with soft references not properly cleared. public class SoftCrash { public static void main(String[] args) { Map<Integer, SoftReference<byte[]>> map = new HashMap<Integer, SoftReference<byte[]>>(); for (int i = 0; i < Integer.MAX_VALUE; i++) { map.put(i, new SoftReference<byte[]>(new byte[100000])); if ((i & 255) == 0) System.out.print("*"); /* * If you comment this block out or run on the client VM, * this program will run indefinitely. If you run it on the * server VM, it quickly crashes with an OutOfMemoryError. */ for (int j = 0; j <= i; j++) { byte[] a = map.get(i).get(); if (a != null) a[0]++; } } } }
09-07-2009