JVM 内存溢出

Question

nginx + memcached + tomcat7.0.39JVM内存配置
export  JAVA_OPTS="$JAVA_OPTS -server
 -Xmx4096M
 -Xms4096M
 -Xmn1000M
 -XX:PermSize=400M
 -XX:MaxPermSize=400M
 -Xss256K 
 -XX:SurvivorRatio=1
 -XX:+UseConcMarkSweepGC
 -XX:+UseParNewGC
 -XX:+CMSParallelReEnabled 
 -XX:+UseCMSCompactAtFullCollection
 -XX:CMSFullGCsBeforeCompaction=0
 -XX:+CMSClassUnloadingEnabled
 -XX:LargePageSizeInBytes=128M
 -XX:+UseFastAccessorMethods
 -XX:+UseCMSInitiatingOccupancyOnly
 -XX:CMSInitiatingOccupancyFraction=70
 -XX:SoftRefLRUPolicyMSPerMB=0
 -XX:+PrintClassHistogram
 -XX:+PrintGCDetails
 -XX:+PrintGCTimeStamps
 -XX:+PrintHeapAtGC
 -Xloggc:log/gc.log
 -XX:ParallelGCThreads=4 "
4台PC Server的物理内存都是12GB，单台部署2个tomcat。
现在做一个工厂电算化的项目，并发数460，月数据量10KK；现在正在项目实施阶段，正常时JVM内存使用的各项参数都十分正常，但是整个集群中的服务不定时的同时出现JVM内存溢出。
如图：
<IMG src="file:///C:\Users\cll\AppData\Roaming\feiq\RichOle\2174584732.bmp">Sep 03, 2013 2:00:54 PM de.javakaffee.web.msm.LockingStrategy onAfterBackupSession
WARNING: An error occurred during onAfterBackupSession.
net.spy.memcached.internal.CheckedOperationTimeoutException: Timed out waiting for operation - failing node: /10.12.152.21:11211
        at net.spy.memcached.internal.OperationFuture.get(OperationFuture.java:159)
        at de.javakaffee.web.msm.LockingStrategy.onAfterBackupSession(LockingStrategy.java:294)
        at de.javakaffee.web.msm.MemcachedSessionService.backupSession(MemcachedSessionService.java:1062)
        at de.javakaffee.web.msm.RequestTrackingHostValve.backupSession(RequestTrackingHostValve.java:243)
        at de.javakaffee.web.msm.RequestTrackingHostValve.invoke(RequestTrackingHostValve.java:168)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1686)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:722)内存溢出jvm内存memcached