I am writing a client-side Swing application (graphical font designer) on Java 5. Recently, I am running into java.lang.OutOfMemoryError: Java heap space error because I am not being conservative on memory usage. The user can open unlimited number of files, and the program keeps the opened objects in the memory. After a quick research I found Ergonomics in the 5.0 Java Virtual Machine and others saying on Windows machine the JVM defaults max heap size as 64MB.
Given this situation, how should I deal with this constraint?
I could increase the max heap size using command line option to java, but that would require figuring out available RAM and writing some launching program or script. Besides, increasing to some finite max does not ultimately get rid of the issue.
I could rewrite some of my code to persist objects to file system frequently (using database is the same thing) to free up the memory. It could work, but it's probably a lot work too.
If you could point me to details of above ideas or some alternatives like automatic virtual memory, extending heap size dynamically, that will be great.
Ultimately you always have a finite max of heap to use no matter what platform you are running on. In Windows 32 bit this is around 2GB (not specifically heap but total amount of memory per process). It just happens that Java chooses to make the default smaller (presumably so that the programmer can't create programs that have runaway memory allocation without running into this problem and having to examine exactly what they are doing).
So this given there are several approaches you could take to either determine what amount of memory you need or to reduce the amount of memory you are using. One common mistake with garbage collected languages such as Java or C# is to keep around references to objects that you no longer are using, or allocating many objects when you could reuse them instead. As long as objects have a reference to them they will continue to use heap space as the garbage collector will not delete them.
In this case you can use a Java memory profiler to determine what methods in your program are allocating large number of objects and then determine if there is a way to make sure they are no longer referenced, or to not allocate them in the first place. One option which I have used in the past is "JMP" http://www.khelekore.org/jmp/.
If you determine that you are allocating these objects for a reason and you need to keep around references (depending on what you are doing this might be the case), you will just need to increase the max heap size when you start the program. However, once you do the memory profiling and understand how your objects are getting allocated you should have a better idea about how much memory you need.
In general if you can't guarantee that your program will run in some finite amount of memory (perhaps depending on input size) you will always run into this problem. Only after exhausting all of this will you need to look into caching objects out to disk etc. At this point you should have a very good reason to say "I need Xgb of memory" for something and you can't work around it by improving your algorithms or memory allocation patterns. Generally this will only usually be the case for algorithms operating on large datasets (like a database or some scientific analysis program) and then techniques like caching and memory mapped IO become useful.
Run Java with the command-line option -Xmx, which sets the maximum size of the heap.
See here for details.
You could specify per project how much heap space your project wants
Following is for Eclipse Helios/Juno/Kepler:
Right mouse click on
Run As - Run Configuration - Arguments - Vm Arguments,
then add this
-Xmx2048m
Increasing the heap size is not a "fix" it is a "plaster", 100% temporary. It will crash again in somewhere else. To avoid these issues, write high performance code.
Use local variables wherever possible.
Make sure you select the correct object (EX: Selection between String, StringBuffer and StringBuilder)
Use a good code system for your program(EX: Using static variables VS non static variables)
Other stuff which could work on your code.
Try to move with multy THREADING
Big caveat ---- at my office, we were finding that (on some windows machines) we could not allocate more than 512m for Java heap. This turned out to be due to the Kaspersky anti-virus product installed on some of those machines. After uninstalling that AV product, we found we could allocate at least 1.6gb, i.e, -Xmx1600m (m is mandatory other wise it will lead to another error "Too small initial heap") works.
No idea if this happens with other AV products but presumably this is happening because the AV program is reserving a small block of memory in every address space, thereby preventing a single really large allocation.
I would like to add recommendations from oracle trouble shooting article.
Exception in thread thread_name: java.lang.OutOfMemoryError: Java heap space
The detail message Java heap space indicates object could not be allocated in the Java heap. This error does not necessarily imply a memory leak
Possible causes:
Simple configuration issue, where the specified heap size is insufficient for the application.
Application is unintentionally holding references to objects, and this prevents the objects from being garbage collected.
Excessive use of finalizers.
One other potential source of this error arises with applications that make excessive use of finalizers. If a class has a finalize method, then objects of that type do not have their space reclaimed at garbage collection time
After garbage collection, the objects are queued for finalization, which occurs at a later time. finalizers are executed by a daemon thread that services the finalization queue. If the finalizer thread cannot keep up with the finalization queue, then the Java heap could fill up and this type of OutOfMemoryError exception would be thrown.
One scenario that can cause this situation is when an application creates high-priority threads that cause the finalization queue to increase at a rate that is faster than the rate at which the finalizer thread is servicing that queue.
VM arguments worked for me in eclipse. If you are using eclipse version 3.4, do the following
go to Run --> Run Configurations --> then select the project under maven build --> then select the tab "JRE" --> then enter -Xmx1024m.
Alternatively you could do Run --> Run Configurations --> select the "JRE" tab --> then enter -Xmx1024m
This should increase the memory heap for all the builds/projects. The above memory size is 1 GB. You can optimize the way you want.
Yes, with -Xmx you can configure more memory for your JVM.
To be sure that you don't leak or waste memory. Take a heap dump and use the Eclipse Memory Analyzer to analyze your memory consumption.
Follow below steps:
Open catalina.sh from tomcat/bin.
Change JAVA_OPTS to
JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1536m
-Xmx1536m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m
-XX:MaxPermSize=256m -XX:+DisableExplicitGC"
Restart your tomcat
By default for development JVM uses small size and small config for other performance related features. But for production you can tune e.g. (In addition it Application Server specific config can exist) -> (If there still isn't enough memory to satisfy the request and the heap has already reached the maximum size, an OutOfMemoryError will occur)
-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size
-XX:ParallelGCThreads=8
-XX:+CMSClassUnloadingEnabled
-XX:InitiatingHeapOccupancyPercent=70
-XX:+UnlockDiagnosticVMOptions
-XX:+UseConcMarkSweepGC
-Xms512m
-Xmx8192m
-XX:MaxPermSize=256m (in java 8 optional)
For example: On linux Platform for production mode preferable settings.
After downloading and configuring server with this way http://www.ehowstuff.com/how-to-install-and-setup-apache-tomcat-8-on-centos-7-1-rhel-7/
1.create setenv.sh file on folder /opt/tomcat/bin/
touch /opt/tomcat/bin/setenv.sh
2.Open and write this params for setting preferable mode.
nano /opt/tomcat/bin/setenv.sh
export CATALINA_OPTS="$CATALINA_OPTS -XX:ParallelGCThreads=8"
export CATALINA_OPTS="$CATALINA_OPTS -XX:+CMSClassUnloadingEnabled"
export CATALINA_OPTS="$CATALINA_OPTS -XX:InitiatingHeapOccupancyPercent=70"
export CATALINA_OPTS="$CATALINA_OPTS -XX:+UnlockDiagnosticVMOptions"
export CATALINA_OPTS="$CATALINA_OPTS -XX:+UseConcMarkSweepGC"
export CATALINA_OPTS="$CATALINA_OPTS -Xms512m"
export CATALINA_OPTS="$CATALINA_OPTS -Xmx8192m"
export CATALINA_OPTS="$CATALINA_OPTS -XX:MaxMetaspaceSize=256M"
3.service tomcat restart
Note that the JVM uses more memory than just the heap. For example
Java methods, thread stacks and native handles are allocated in memory
separate from the heap, as well as JVM internal data structures.
I read somewhere else that you can try - catch java.lang.OutOfMemoryError and on the catch block, you can free all resources that you know might use a lot of memory, close connections and so forth, then do a System.gc() then re-try whatever you were going to do.
Another way is this although, i don't know whether this would work, but I am currently testing whether it will work on my application.
The Idea is to do Garbage collection by calling System.gc() which is known to increase free memory. You can keep checking this after a memory gobbling code executes.
//Mimimum acceptable free memory you think your app needs
long minRunningMemory = (1024*1024);
Runtime runtime = Runtime.getRuntime();
if(runtime.freeMemory()<minRunningMemory)
System.gc();
Easy way to solve OutOfMemoryError in java is to increase the maximum heap size by using JVM options -Xmx512M, this will immediately solve your OutOfMemoryError. This is my preferred solution when I get OutOfMemoryError in Eclipse, Maven or ANT while building project because based upon size of project you can easily ran out of Memory.
Here is an example of increasing maximum heap size of JVM, Also its better to keep -Xmx to -Xms ration either 1:1 or 1:1.5 if you are setting heap size in your java application.
export JVM_ARGS="-Xms1024m -Xmx1024m"
Reference Link
If you came here to search this issue from REACT NATIVE.
Then i guess you should do this
cd android/ && ./gradlew clean && cd ..
Add this line to your gradle.properties file
org.gradle.jvmargs=-Xmx2048m -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8
It should work. You can change MaxPermSize accordingly to fix your heap problem
I have faced same problem from java heap size.
I have two solutions if you are using java 5(1.5).
just install jdk1.6 and go to the preferences of eclipse and set the jre path of jav1 1.6 as you have installed.
Check your VM argument and let it be whatever it is.
just add one line below of all the arguments present in VM arguments as
-Xms512m -Xmx512m -XX:MaxPermSize=...m(192m).
I think it will work...
If you need to monitor your memory usage at runtime, the java.lang.management package offers MBeans that can be used to monitor the memory pools in your VM (eg, eden space, tenured generation etc), and also garbage collection behaviour.
The free heap space reported by these MBeans will vary greatly depending on GC behaviour, particularly if your application generates a lot of objects which are later GC-ed. One possible approach is to monitor the free heap space after each full-GC, which you may be able to use to make a decision on freeing up memory by persisting objects.
Ultimately, your best bet is to limit your memory retention as far as possible whilst performance remains acceptable. As a previous comment noted, memory is always limited, but your app should have a strategy for dealing with memory exhaustion.
In android studio add/change this line at the end of gradle.properties (Global Properties):
...
org.gradle.jvmargs=-XX\:MaxHeapSize\=1024m -Xmx1024m
if it doesn't work you can retry with bigger than 1024 heap size.
add the below code inside android/gradle.properties:
org.gradle.jvmargs=-Xmx4096m -XX:MaxPermSize=4096m -XX:+HeapDumpOnOutOfMemoryError
org.gradle.daemon=true
org.gradle.parallel=true
org.gradle.configureondemand=true
Note that if you need this in a deployment situation, consider using Java WebStart (with an "ondisk" version, not the network one - possible in Java 6u10 and later) as it allows you to specify the various arguments to the JVM in a cross platform way.
Otherwise you will need an operating system specific launcher which sets the arguments you need.
In my case it solved by assigning more memory to Shared build process heap size in intellij settings.
Go to intellij settings > Compiler > Shared build process heap size
Regarding to netbeans, you could set max heap size to solve the problem.
Go to 'Run', then --> 'Set Project Configuration' --> 'Customise' --> 'run' of its popped up window --> 'VM Option' --> fill in '-Xms2048m -Xmx2048m'.
If you are using Android Studio just add these lines with gradle.properties file
org.gradle.jvmargs=-Xmx2048m -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8
Android Studio
File -> Invalidate Caches and Restart solved it for me :)
If this issue is happening in Wildfly 8 and JDK1.8,then we need to specify MaxMetaSpace settings instead of PermGen settings.
For example we need to add below configuration in setenv.sh file of wildfly.
JAVA_OPTS="$JAVA_OPTS -XX:MaxMetaspaceSize=256M"
For more information, please check Wildfly Heap Issue
If you keep on allocating & keeping references to object, you will fill up any amount of memory you have.
One option is to do a transparent file close & open when they switch tabs (you only keep a pointer to the file, and when the user switches tab, you close & clean all the objects... it'll make the file change slower... but...), and maybe keep only 3 or 4 files on memory.
Other thing you should do is, when the user opens a file, load it, and intercept any OutOfMemoryError, then (as it is not possible to open the file) close that file, clean its objects and warn the user that he should close unused files.
Your idea of dynamically extending virtual memory doesn't solve the issue, for the machine is limited on resources, so you should be carefull & handle memory issues (or at least, be carefull with them).
A couple of hints i've seen with memory leaks is:
--> Keep on mind that if you put something into a collection and afterwards forget about it, you still have a strong reference to it, so nullify the collection, clean it or do something with it... if not you will find a memory leak difficult to find.
--> Maybe, using collections with weak references (weakhashmap...) can help with memory issues, but you must be carefull with it, for you might find that the object you look for has been collected.
--> Another idea i've found is to develope a persistent collection that stored on database objects least used and transparently loaded. This would probably be the best approach...
Java OOM Heap space issue can also arise when your DB connection pool got full.
I faced this issue because of my Hikari Connection pool (when upgraded to Spring boot 2.4.*) was full and not able to provide connections anymore (all active connections are still pending to fetch results from database).
Issue is some of our native queries in JPA Repositories contain ORDER BY ?#{#pageable} which takes a very long time to get results when upgraded.
Removed ORDER BY ?#{#pageable} from all the native queries in JPA repositories and OOM heap space issue along with connection pool issue got resolved.
If this error occurs right after execution of your junit tests, then you should execute Build -> Rebuild Project.
If this error comes up during APK generation in react-native, cd into the android folder in your project and do:
./gradlew clean
then
./gradlew assembleRelease
If error persists, then, restart your machine.
In Intellij, it worked for me just by giving the "Build Project"
If everything else fails, in addition to increasing the max heap size try also increasing the swap size. For Linux, as of now, relevant instructions can be found in https://linuxize.com/post/create-a-linux-swap-file/.
This can help if you're e.g. compiling something big in an embedded platform.
I'm debugging a fairly large project I've been working on (but did not originally create) and I've noticed that sometimes it crashes with an OutOfMemoryError. The code is loading a lot of data from files so this isn't entirely surprising in general.
However, what confuses me is that I'm using VisualVM 1.3.4 to profile the program, and it behaves inconsistently. Most times I've run it, the heap gradually expands up to about 2GB (the computer has 16GB of RAM; it's for academic research) with the used heap spiking higher and higher underneath it. Around 2GB, it will crash. The program isn't proccessing more information as time goes on though, so it shouldn't grow the heap to 2GB in just a few minutes.
Sometimes, though, I get a sudden crash after about 30 seconds, with a heap size of 250MB and only about 100MB in use. How am I getting a java.lang.OutOfMemoryError: Java heap space if my heap isn't full?
Edit: I'm using Eclipse to run the program, and I have the VisualVM plugin so it gets launched automatically. Also, I'm using Java 7.
Start the application with the VM argument -XX:+HeapDumpOnOutOfMemoryError.
Analyse the Heap Dump and find out what is causing the issue.
Eclipse MAT is an excellent tool for finding out such issues.
you need to setup the JVMs min and max heap memory
set JAVA_OPTS="-Xms128m -Xmx256m"
something like that but with bigger values like 2G, 4G whatever
LE: As you all know you can't force JVM to run the garbage collector (even though you can ask for it), but there are some ways of convincing it to get rid of some items by null-ing their references. Another thing to watch is the database object that might be lazy initialised. That error could appear when you try to create an object exceding the max heap memory.
Another ideea could be some retarded developer that programatically threw the OutOfMemoryError in some method for some retarded reason. When you reach that part of code, that's what you get (search the project)
There can be at least 2 reasons for the application to crash with OutOfMemoryError.
Your java heap is just too small for the amount of data it needs to process. Then you can either increase it as suggested Matei, or analyze heap dump as suggest Ajay.
Your application leaks memory. Which means that it leaves some unneeded data in memory after processing it. Then increasing heap will not help in the long run. And your options are either heap dump analysis (again) or specialised memory leak detection tool, such as Plumbr
Turned out the crash was caused by using the OpenJDK JRE rather than Oracle's JRE. I don't know exactly what the bug is in OpenJDK that makes it crash like this, but changing to Oracle's JRE ultimately solved the problem.
(I was using OpenJDK because I'm on a Linux computer that someone was using for open-source work before me. When I mentioned the crash to him he had the idea that that might be the cause. He was right.)
Do you have a 32bit operative system without large memory support (PAE on win, huge mem kernel on linux...)? If yes, you may encounter the 2GB memory segment limit per process on 32 bit systems.
As a work around, try to set the JVM parameter -Xss192k to dispose 192kb of stack space per thread, and the parameter -Xmx1024m to use no more than 1GB of heap.
My application currently consumes quite a lot of memory because it is running physics simulations. The issue is that consistently, at the 51st simulation, Java will throw an error usually because of a heap space out of memory (my program eventually runs thousands of simulations).
Is there anyway I can not just increase the heap space but modify my program so that the heap space is cleared after every run so that I can run an arbitrary number of simulations?
Edit: Thanks guys. Turns out the simulator software wasn't clearing the information after every run and I had those runs all stored in an ArrayList.
There is no way to dynamically increase the heap programatically since the heap is allocated when the Java Virtual Machine is started.
However, you can use this command
java -Xmx1024M YourClass
to set the memory to 1024
or, you can set a min max
java -Xms256m -Xmx1024m YourClassNameHere
If you are using a lot of memory and facing memory leaks, then you might want to check if you are using a large number of ArrayLists or HashMaps with many elements each.
An ArrayList is implemented as a dynamic array. The source code from Sun/Oracle shows that when a new element is inserted into a full ArrayList, a new array of 1.5 times the size of the original array is created, and the elements copied over. What this means is that you could be wasting up to 50% of the space in each ArrayList you use, unless you call its trimToSize method. Or better still, if you know the number of elements you are going to insert before hand, then call the constructor with the initial capacity as its argument.
I did not examine the source code for HashMap very carefully, but at a first glance it appears that the array length in each HashMap must be a power of two, making it another implementation of a dynamic array. Note that HashSet is essentially a wrapper around HashMap.
There are a variety of tools that you can use to help diagnose this problem. The JDK includes JVisualVM that will allow you to attach to your running process and show what objects might be growing out of control. Netbeans has a wrapper around it that works fairly well. Eclipse has the Eclipse Memory Analyzer which is the one I use most often, just seems to handle large dump files a bit better. There's also a command line option, -XX:+HeapDumpOnOutOfMemoryError that will give you a file that is basically a snapshot of your process memory when your program crashed. You can use any of the above mentioned tools to look at it, it can really help a lot when diagnosing these sort of problems.
Depending on how hard the program is working, it may be a simple case of the JVM not knowing when a good time to garbage collect may be, you might also look into the parallel garbage collection options as well.
I also faced the same problem.I resolved by doing the build by following steps as.
-->Right click on the project select RunAs ->Run configurations
Select your project as BaseDirectory. In place of goals give eclipse:eclipse install
-->In the second tab give -Xmx1024m as VM arguments.
I would like to add that this problem is similar to common Java memory leaks.
When the JVM garbage collector is unable to clear the "waste" memory of your Java / Java EE application over time, OutOfMemoryError: Java heap space will be the outcome.
It is important to perform a proper diagnostic first:
Enable verbose:gc. This will allow you to understand the memory growing pattern over time.
Generate and analyze a JVM Heap Dump. This will allow you to understand your application memory footprint and pinpoint the source of the memory leak(s).
You can also use Java profilers and runtime memory leak analyzer such as Plumbr as well to help you with this task.
Try adding -Xmx for more memory ( java -Xmx1024M YourClass ), and don't forget to stop referencing variables you don't need any more (memory leaks).
Are you keeping references to variables that you no longer need (e.g. data from the previous simulations)? If so, you have a memory leak. You just need to find where that is happening and make sure that you remove the references to the variables when they are no longer needed (this would automatically happen if they go out of scope).
If you actually need all that data from previous simulations in memory, you need to increase the heap size or change your algorithm.
Java is supposed to clear the heap space for you when all of the objects are no longer referenced. It won't generally release it back to the OS though, it will keep that memory for it's own internal reuse. Maybe check to see if you have some arrays which are not being cleared or something.
No. The heap is cleared by the garbage collector whenever it feels like it. You can ask it to run (with System.gc()) but it is not guaranteed to run.
First try increasing the memory by setting -Xmx256m
I have a Java app that imports another jar as a library and calls its main method as shown below. But someApp is a very large process and constantly throws an OutOfMemoryError. No matter what I set my Java apps heap size to, someApp does not seem to share the allocated memory.
try {
someApp.main(args);
} catch (Exception ex) {
}
How do I get someApp to allocate more heap space? Can I use processBuilder? What do I do?
Thanks.
As it stands at the moment, you're merely calling a class from another application within your own Java process. This is exactly the same as you'd do for calling a "library method" (the term has no technical difference, you're simply invoking a method on an object of a class that can be resolved by your classloader).
So right now, someApp is running in the same JVM as your own application, and will share its maximum heap size. This can be increase with the JVM argument -Xmx (e.g. -Xmx2048m for a 2GB max heap), though it sounds like you're doing this already withotu success.
It would be possible to launch someApp in a separate Java process, which would allow you to configure separate JVM arguments and thus give it a separate heap size.
However, I don't think this is going to help much. If you're unable to get this application to run in the same JVM, regardless of your heap limit, there's nothing that would suggest it would work in a difference JVM. For example, if you're running with a 2.5GB heap and still running out of memory, running your own app with a 0.5GB heap and spawning a separate JVM with 2GB heap will not solve the problem, as something is still running out of memory. (In fact, separate memory pools make an OOME slightly more likely since there are two distinct chunks of free space, whereas in the former case both applications can benefit from the same pool of free space).
I suggest you verify that your heap sizes really are being picked up (connecting via JMX using JConsole or JVisualVM will quickly let you see how big the max heap size is). If you're really still running out of memory with large heaps, it sounds like someApp has a memory leak (or a requirement for an even larger heap). Capturing a heap dump in this case, with the JVM argument -XX:+HeapDumpOnOutOfMemoryError, will allow you to inspect the heap with an external tool and determine what's filling the memory.
Hopefully you've simply failed to increase the heap size correctly, as if the application really is failing with a large heap there are no simple solutions.
Unless someApp itself is building a new process, this will already be in the same process as your calling code, so it should be affected by whatever heap configuration you've set when starting up the JVM.
Have you kept track of how much memory the process is actually taking?
This doesn't make sense, unless you're running into OS limitations on how much memory you can allocate to a single Java process on your OS (see Java maximum memory on Windows XP)
Short of that, the way you're invoking someApp, it acts as a regular library. The main method acts like any other method.
Have you tried debugging the OutOfMemoryError? There may be something obscure that the app doesn't like about being invoked from your application...
If the jar you are importing is authored by you and could be more efficient, then modify it. It sounds like the problem you are having is loading in a shotty package. If this is a 3rd party package and you are allowed to modify it, poke around in the code and find where there might be limitations, change it, and rebuild it.