[jboss-user] [JBoss Cache: Core Edition] - Excessive ReentrantLock$NonfairSync objects

[molsen-ee]

I'm using jboss-cache (jbosscache-core-2.1.1.GA) to implement a cache on a Tomcat/Apache environment and am having some issues with memory usage. 

When I have the Isolation level set to anything other than "NONE" there is an excessive number of objects relating to ConcurrentHashMap's created and residing in memory.  When 400k Nodes' are created there are over 7 million ConcurrentHashMap structures, approximately 16 per node.  See the jmap histo dump below for the memory usage.


  | num   #instances    #bytes  class name
  | --------------------------------------
  |   1:   7058684   225877888  java.util.concurrent.ConcurrentHashMap$Segment
  |   2:   7058738   169409712  java.util.concurrent.locks.ReentrantLock$NonfairSync
  |   3:   7058684   116611080  [Ljava.util.concurrent.ConcurrentHashMap$HashEntry;
  |   4:    443647    35648184  [Ljava.util.HashMap$Entry;
  |   5:    441170    35293456  [Ljava.util.concurrent.ConcurrentHashMap$Segment;
  |   6:    441115    24702440  org.jboss.cache.lock.ReadWriteLockWithUpgrade
  |   7:    441115    21173520  org.jboss.cache.UnversionedNode
  |   8:    443357    17734280  java.util.HashMap
  |   9:    441170    17646800  java.util.concurrent.ConcurrentHashMap
  |  10:    441115    17644600  org.jboss.cache.invocation.NodeInvocationDelegate
  |  11:    455905    11396456  [Ljava.lang.Object;
  |  12:    460983    11063592  java.util.HashMap$Entry
  |  13:    270774    11019496  [C
  |  14:    442649    10623576  java.util.ArrayList
  |  15:    441377    10593048  java.util.concurrent.ConcurrentHashMap$HashEntry
  |  16:    441142    10587408  java.util.RegularEnumSet
  |  17:    441116    10586784  org.jboss.cache.Fqn
  |  18:    441115    10586760  org.jboss.cache.lock.IdentityLock
  |  19:    441117     7057872  org.jboss.cache.util.concurrent.ConcurrentHashSet
  |  20:    441115     7057840  org.jboss.cache.lock.LockStrategyRepeatableRead
  |  21:    441115     7057840  org.jboss.cache.lock.ReadWriteLockWithUpgrade$WriterLock
  |  22:    441115     7057840  org.jboss.cache.lock.ReadWriteLockWithUpgrade$ReaderLock
  |  23:    441115     7057840  org.jboss.cache.lock.LockMap
  | 

The cache is initialized and populated in a tomcat request filter when the tomcat server is first started.  The cache seems to work properly but it is consuming incredible amounts of memory.

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