java lang OutOfMemoryError GC overhead limit exceeded

Question

I am getting this error in a program that creates several  hundreds of thousands  HashMap objects with a few  15-20  text entries each  These Strings have all to be collected  without breaking up into smaller amounts  before being submitted to a database   According to Sun  the error happens  if too much time is being spent in garbage collection  if more than 98  of the total time is spent in garbage collection and less than 2  of the heap is recovered  an OutOfMemoryError will be thrown     Apparently  one could use the command line to pass arguments to the JVM for   Increasing the heap size  via  -Xmx1024m   or more   or  Disabling the error check altogether  via  -XX -UseGCOverheadLimit     The first approach works fine  the second ends up in another java lang OutOfMemoryError  this time about the heap   So  question  is there any programmatic alternative to this  for the particular use case  i e   several small HashMap objects   If I use the HashMap clear   method  for instance  the problem goes away  but so do the data stored in the HashMap   -   The issue is also discussed in a related topic in StackOverflow

User · Answer

The following worked for me  Just add the following snippet   dexOptions           javaMaxHeapSize  4g      To your build gradle   android       compileSdkVersion 23     buildToolsVersion  23 0 1       defaultConfig           applicationId  yourpackage          minSdkVersion 14         targetSdkVersion 23         versionCode 1         versionName  1 0           multiDexEnabled true            buildTypes           release               minifyEnabled false             proguardFiles getDefaultProguardFile  proguard-android txt     proguard-rules pro                       packagingOptions               dexOptions           javaMaxHeapSize  4g

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If you have java8  and you can use the G1 Garbage Collector  then run your application with    -XX  UseG1GC -XX  UseStringDeduplication   This tells the G1 to find similar Strings and keep only one of them in memory  and the others are only a pointer to that String in memory   This is useful when you have a lot of repeated strings  This solution may or not work and depends on each application   More info on  https   blog codecentric de en 2014 08 string-deduplication-new-feature-java-8-update-20-2  http   java-performance info java-string-deduplication

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Don t store the whole structure in memory while waiting to get to the end    Write intermediate results to a temporary table in the database instead of hashmaps - functionally  a database table is the equivalent of a hashmap  i e  both support keyed access to data  but the table is not memory bound  so use an indexed table here rather than the hashmaps   If done correctly  your algorithm should not even notice the change - correctly here means to use a class to represent the table  even giving it a put key  value  and a get key  method just like a hashmap   When the intermediate table is complete  generate the required sql statement s  from it instead of from memory

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Ummm    you ll either need to     Completely rethink your algorithm  amp  data-structures  such that it doesn t need all these little HashMaps  Create a facade which allows you page those HashMaps in-and-out of memory as required  A simple LRU-cache might be just the ticket  Up the memory available to the JVM  If necessary  even purchasing more RAM might be the quickest  CHEAPEST solution  if you have the management of the machine that hosts this beast  Having said that  I m generally not a fan of the  throw more hardware at it  solutions  especially if an alternative algorithmic solution can be thought up within a reasonable timeframe  If you keep throwing more hardware at every one of these problems you soon run into the law of diminishing returns    What are you actually trying to do anyway  I suspect there s a better approach to your actual problem

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takrl  The default setting for this option is   java -XX  UseConcMarkSweepGC   which means  this option is not active by default  So when you say you used the option    XX UseConcMarkSweepGC   I assume you were using this syntax   java -XX  UseConcMarkSweepGC   which means you were explicitly activating this option  For the correct syntax and default settings of Java HotSpot VM Options   this  document

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In case of the error       Internal compiler error  java lang OutOfMemoryError  GC overhead limit exceeded at java lang AbstractStringBuilder     increase the java heap space to 2GB i e   -Xmx2g

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You need to increase the memory size in Jdeveloper go to setDomainEnv cmd   set WLS HOME  WL HOME  server set XMS SUN 64BIT 256 set XMS SUN 32BIT 256 set XMX SUN 64BIT 3072 set XMX SUN 32BIT 3072 set XMS JROCKIT 64BIT 256 set XMS JROCKIT 32BIT 256 set XMX JROCKIT 64BIT 1024 set XMX JROCKIT 32BIT 1024  if   JAVA VENDOR     Sun        set WLS MEM ARGS 64BIT -Xms256m -Xmx512m     set WLS MEM ARGS 32BIT -Xms256m -Xmx512m   else       set WLS MEM ARGS 64BIT -Xms512m -Xmx512m     set WLS MEM ARGS 32BIT -Xms512m -Xmx512m   and  set MEM PERM SIZE 64BIT -XX PermSize 256m set MEM PERM SIZE 32BIT -XX PermSize 256m  if   JAVA USE 64BIT     true        set MEM PERM SIZE  MEM PERM SIZE 64BIT     else       set MEM PERM SIZE  MEM PERM SIZE 32BIT     set MEM MAX PERM SIZE 64BIT -XX MaxPermSize 1024m set MEM MAX PERM SIZE 32BIT -XX MaxPermSize 1024m

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For the record  we had the same problem today  We fixed it by using this option   -XX -UseConcMarkSweepGC   Apparently  this modified the strategy used for garbage collection  which made the issue disappear

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For this use below code in your app gradle file under android closure   dexOptions       javaMaxHeapSize  4g

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If you re creating hundreds of thousands of hash maps  you re probably using far more than you actually need  unless you re working with large files or graphics  storing simple data shouldn t overflow the Java memory limit   You should try and rethink your algorithm   In this case  I would offer more help on that subject  but I can t give any information until you provide more about the context of the problem

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Use alternative HashMap implementation  Trove   Standard Java HashMap has  12x memory overhead  One can read details here

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The parallel collector will throw an OutOfMemoryError if too much time is being spent in garbage collection  In particular  if more than 98  of the total time is spent in garbage collection and less than 2  of the heap is recovered  OutOfMemoryError will be thrown  This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small  If necessary  this feature can be disabled by adding the option -XX -UseGCOverheadLimit to the command line

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You re essentially running out of memory to run the process smoothly  Options that come to mind   Specify more memory like you mentioned  try something in between like -Xmx512m first Work with smaller batches of HashMap objects to process at once if possible If you have a lot of duplicate strings  use String intern   on them before putting them into the HashMap Use the HashMap int initialCapacity  float loadFactor  constructor to tune for your case

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This helped me to get rid of this error This option disables  -XX  DisableExplicitGC

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Fix memory leaks in your application with help of profile tools like eclipse MAT  or VisualVM  With JDK 1 7 x or later versions  use G1GC  which spends 10  on garbage collection unlike 2  in other GC algorithms   Apart from setting heap memory with -Xms1g -Xmx2g   try     -XX  UseG1GC  -XX G1HeapRegionSize n   -XX MaxGCPauseMillis m   -XX ParallelGCThreads n   -XX ConcGCThreads n    Have a look at oracle article for fine-tuning these parameters    Some question related to G1GC in SE   Java 7  JDK 7  garbage collection and documentation on G1  Java G1 garbage collection in production  Agressive garbage collector strategy

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For my case increasing the memory using -Xmx option was the solution    I had a 10g file read in java and each time I got the same error  This happened when the value in the RES column in top command reached to the value set in -Xmx option  Then by increasing the memory using -Xmx option everything went fine   There was another point as well  When I set JAVA OPTS or CATALINA OPTS in my user account and increased the amount of memory again I got the same error  Then  I printed the value of those environment variables in my code which gave me different values than what I set  The reason was that Tomcat was the root for that process and then as I was not a su-doer I asked the admin to increase the memory in catalina sh in Tomcat

[java] java.lang.OutOfMemoryError: GC overhead limit exceeded

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