What is going on with java GC? PermGen space is filling up?
garbage-collection, java, jvm
Solution
This will happen if your memory is fragmented, or there is nothing to clean up. It happens often when you are close to the maximum memory size.
I have never heard of anyone needing a 2 G per gen size. Are you sure its not the young and tenured spaces you need to be looking at?
BTW: intern()ed String are placed in the main heap spaces in Java 7. Before Java 7, they used to be placed into the perm gen space, which makes it a bad idea to make too much data interned()
Problem
I dont know what is going on with my java process. This process is an indexing process. It reads documents from a set of zip files, and adds them to the lucene index. The GC log shows that it is just running continuously Full GC. ``` 4959.569: [Full GC 19960K->19960K(10617856K), 0.1648590 secs] 4959.764: [Full GC 19960K->19960K(10617856K), 0.1650240 secs] 4959.959: [Full GC 19960K->19960K(10617856K), 0.1649380 secs] 4960.154: [Full GC 19960K->19960K(10617856K), 0.1650000 secs] 4960.350: [Full GC 19960K->19960K(10617856K), 0.1648900 secs] ``` As far as I can interpret these lines, the size of objects before and after is around 19M, but why is it running it like all the time? The thread dump looks like this: ``` ........[Unloading class sun.reflect.GeneratedConstructorAccessor1] [Unloading class sun.reflect.GeneratedConstructorAccessor2] [Unloading class sun.reflect.GeneratedConstructorAccessor3] 2012-01-13 12:55:24 Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.4-b02 mixed mode): "org.cxv.CXVIndexer.main()" prio=10 tid=0x00007f4540474000 nid=0x4b15 waiting on condition [0x00007f453f5ed000] java.lang.Thread.State: RUNNABLE at org.apache.lucene.index.DocFieldProcessorPerThread.abort(DocFieldProcessorPerThread.java:72) at org.apache.lucene.index.DocumentsWriter.abort(DocumentsWriter.java:424) - locked <0x000000034ab44fb8> (a org.apache.lucene.index.DocumentsWriter) at org.apache.lucene.index.DocumentsWriter.flush(DocumentsWriter.java:659) - locked <0x000000034ab44fb8> (a org.apache.lucene.index.DocumentsWriter) at org.apache.lucene.index.IndexWriter.doFlush(IndexWriter.java:3623) - locked <0x000000034aacf660> (a org.apache.lucene.index.IndexWriter) at org.apache.lucene.index.IndexWriter.flush(IndexWriter.java:3588) at org.apache.lucene.index.IndexWriter.closeInternal(IndexWriter.java:1858) at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1822) at org.cxv.IndexCreator.close(IndexCreator.java:25) at org.cxv.CXVIndexer.doIndexing(CXVIndexer.java:41) at org.cxv.CXVIndexer.main(CXVIndexer.java:75) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:297) at java.lang.Thread.run(Thread.java:662) "Low Memory Detector" daemon prio=10 tid=0x00007f4540003800 nid=0x4b0a runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread1" daemon prio=10 tid=0x00007f4540001000 nid=0x4b09 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread0" daemon prio=10 tid=0x000000004032d800 nid=0x4b08 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" daemon prio=10 tid=0x000000004032b800 nid=0x4b07 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Surrogate Locker Thread (Concurrent GC)" daemon prio=10 tid=0x0000000040329800 nid=0x4b06 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Finalizer" daemon prio=10 tid=0x000000004030c800 nid=0x4b05 in Object.wait() [0x00007f453fdfc000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000034a6613a8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <0x000000034a6613a8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159) "Reference Handler" daemon prio=10 tid=0x0000000040305000 nid=0x4b04 in Object.wait() [0x00007f453fefd000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000034a6627c0> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:485) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116) - locked <0x000000034a6627c0> (a java.lang.ref.Reference$Lock) "main" prio=10 tid=0x0000000040111000 nid=0x4af7 in Object.wait() [0x00007f4563c79000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000034aadf6f8> (a java.lang.Thread) at java.lang.Thread.join(Thread.java:1186) - locked <0x000000034aadf6f8> (a java.lang.Thread) at org.codehaus.mojo.exec.ExecJavaMojo.joinThread(ExecJavaMojo.java:415) at org.codehaus.mojo.exec.ExecJavaMojo.joinNonDaemonThreads(ExecJavaMojo.java:405) at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:317) at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:107) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59) at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183) at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:319) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156) at org.apache.maven.cli.MavenCli.execute(MavenCli.java:534) at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196) at org.apache.maven.cli.MavenCli.main(MavenCli.java:141) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290) at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230) at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409) at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352) "VM Thread" prio=10 tid=0x00000000402fe000 nid=0x4b03 runnable "Gang worker#0 (Parallel GC Threads)" prio=10 tid=0x0000000040120000 nid=0x4af8 runnable "Gang worker#1 (Parallel GC Threads)" prio=10 tid=0x0000000040122000 nid=0x4af9 runnable "Gang worker#2 (Parallel GC Threads)" prio=10 tid=0x0000000040123800 nid=0x4afa runnable "Gang worker#3 (Parallel GC Threads)" prio=10 tid=0x0000000040125800 nid=0x4afb runnable "Gang worker#4 (Parallel GC Threads)" prio=10 tid=0x0000000040127800 nid=0x4afc runnable "Gang worker#5 (Parallel GC Threads)" prio=10 tid=0x0000000040129000 nid=0x4afd runnable "Gang worker#6 (Parallel GC Threads)" prio=10 tid=0x000000004012b000 nid=0x4afe runnable "Gang worker#7 (Parallel GC Threads)" prio=10 tid=0x000000004012d000 nid=0x4aff runnable "Concurrent Mark-Sweep GC Thread" prio=10 tid=0x0000000040220800 nid=0x4b02 runnable "Gang worker#0 (Parallel CMS Threads)" prio=10 tid=0x000000004021c800 nid=0x4b00 runnable "Gang worker#1 (Parallel CMS Threads)" prio=10 tid=0x000000004021e800 nid=0x4b01 runnable "VM Periodic Task Thread" prio=10 tid=0x000000004033a000 nid=0x4b0b waiting on condition JNI global references: 1154 Heap par new generation total 153344K, used 0K [0x0000000340000000, 0x000000034a660000, 0x000000034a660000) eden space 136320K, 0% used [0x0000000340000000, 0x0000000340000000, 0x0000000348520000) from space 17024K, 0% used [0x00000003495c0000, 0x00000003495c0000, 0x000000034a660000) to space 17024K, 0% used [0x0000000348520000, 0x0000000348520000, 0x00000003495c0000) concurrent mark-sweep generation total 10464512K, used 19960K [0x000000034a660000, 0x00000005c91a0000, 0x0000000780000000) concurrent-mark-sweep perm gen total 2097152K, used 2097151K [0x0000000780000000, 0x0000000800000000, 0x0000000800000000) ``` From the thread dump, it looks like the 2G perm gen is filling up. Does it really need that much space for perm gen?