I have defined -Xmsx 1.3GB in the java VM parameters and my Eclipse does not allow more than this, when running the application I got the below exception:
Exception in thread "Thread-3" java.lang.OutOfMemoryError: Java heap space
What can I do?
You can set the maximum memory eclipse uses with -mx1300m or the like. This limitation will be because you are running 32-bit java on Windows. On a 64-bit OS, you won't have this problem.
However, its the maximum memory size you set for each application in eclipse which matters. What have you set in your run options in eclipse?
Your question is very unclear:
Are you running the application in a new JVM?
Did you set the -Xmx / -Xms parameters in the launcher for the child JVM?
If the answer to either of those questions is "no", then try doing ... both. (In particular, if you don't set at least -Xmx for the child JVM, you'll get the default heap size which is relatively small.)
If the answer to both of those questions is "yes", then the problem is that you are running into the limits of your hardware and/or operating system configuration:
On a typical 32bit Windows, a user process can only address a total 2**31 bytes of virtual memory, and some of that will be used by the JVM binaries, native libraries and various non-heap memory allocations. (On a 32 bit Linux, I believe you can have up to 2**31 + 2**30). The "fix" for this is to use a 64bit OS and a 64bit JVM.
In addition, a JVM is limited on the amount of memory that it can request by the resources of the OS'es virtual memory subsystem. This is typically bounded by the sum of the available RAM and the size of the disc files / partitions used for paging. The "fix" for this is to increase the size of the paging file / partition. Adding more RAM would probably be a good idea too.
You may want to look at the aggressive Heap option http://java.sun.com/docs/hotspot/gc1.4.2/#4.2.2.%20AggressiveHeap|outline
It solved a similiar issue for me.
Related
Just a question that i wasn't able to find an answer too after a lot of searching.
Can a single instance of a java software use more than 10GB of ram on a server that has more than 128GB of RAM installed and still run fine without any issues? Or are there any limits on memory usage of a single instance of process.
The maximum heap size for the Java Virtual Machine will most likely be constrained by your OS. Theoretically, if you have a 64-bit machine, you can allocate the JVM a heap size of 2^64. Since you have 128GB of memory, this is most likely your upper limit. Although, without knowing what your OS is, other constraints may arise.
edit: this link contains a guide to helping you setup your memory limits for your JVM on some different operating systems -> Guide
If I have 16 GB of RAM on my machine, how much can I allocate to a java command line program I'm executing? I assume java -Xmx 16g... will crash my system?
EDIT:
In light of the comments, I tried java -Xmx16g..., and it did not crash my machine. The program still ran out of memory. I tried java -Xmx32g..., which did crash my machine.
From the comments below (which have been really enlightening), I guess I just need to keep playing around with the allocations.
The size the heap memory of the virtual machine is controlled by the options - Xms
and - Xmx .
The first specifies the initial heap size and the second maximum size.
The allocation is done within the JVM itself ,and not on the OS. As more memory is needed, the JVM allocates a block of memory until the Xmx is reached.
If you need more than that, an OutOfMemoryError is thrown.
It is common to use the same value for Xms and Xmx,
causing the VM to allocate memory in the operating system only at the beginning of an execution,
not depending on the OS specific behavior.
In your case, since you set 32g as your Xmx and your system crashed, it seems you don't have this memory (swap + memory ram)
If you manually change the virtual memory size of your system, the configuration will work.
It is not possible for your OS to allocate more than 16GB and therefore your system crash. Apart from XMX and XMS that is stated in another answer there is also an -XX:+AggressiveHeap option which inspects the machine resources (size of memory and number of processors) and attempts to set various parameters to be optimal for long-running, memory allocation-intensive jobs
I am working on java application and I have set the following configurations in the VM option
-Xms and -Xmx options are set to 1024m
-XX:MaxPermSize=128m Hardware :32 bit Windows 7 system with 2GB ram.
I often encounter with java out of swap space error. What could be the reason? Please help me.
The reason is that your operating system is not configured with enough swap space for the job mix that you are running. Swap space is an area on disc where the operating system puts copies memory pages when there are more virtual memory pages than physical memory pages.
So what has happened is that your JVM has asked for more virtual memory than the operating system can give it.
(Updated to include Peter's comments)
Some possible fixes:
Add more physical memory assuming that the hardware and OS allow this. (In this case, the answer the OS should allow it ...)
Configure the system with more swap space.
Kill some of the other non-essential applications and services running on the machine.
Change the Java application's JVM options to reduce the heap size.
The Java release notes under "Hotspot VM" say about this exact error;
If you see this symptom, consider increasing the available swap space
by allocating more of your disk for virtual memory and/or by limiting
the number of applications you run simultaneously. You can also
decrease your usage of memory by reducing the value of the -Xmx flag,
which limits the size of the Java object heap.
In other words, your machine is doing too many other things using up memory to be able to supply the 1GB you're telling the Java VM that it should be able to use.
I am running a server with the following attributes:
Windows Server 2008 R2 Standard - 64bit
4gb RAM
I am trying to set the heap size to 3gb for an application. I am using the flags -Xmx3G -Xms3G. Running with the flags results in the following error:
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.
I have been playing with the setting to see what my ceiling is and found that 1568 is my ceiling. What am I missing?
How much physical memory is available on your system (out of the original 4 GB)? It sounds like your system doesn't have 3GB of physical memory available when the vm starts up.
Remember that the JVM needs more memory than is allocated to the heap -- there are other data structures as well (thread stacks, etc) that also need memory. So the settings you are providing attempt to use more than 3GB of memory.
Also, are you using a 64-bit jvm? The practical limit for heap size on a 32-bit vm is 1.4 to 1.6 gigabytes according to this document.
Java requires continuous virtual memory on startup. On windows, 32-bit application run in an 32-bit emulated environment so you don't get much more continuous memory than you would in a 32-bit OS. c.f. on Solaris you get over 3 GB virtual memory for 32-bit Java.
I suggest you use the 64-bit version of Java as this will make use of all the memory you have. You still need to have free memory but the larger address space doesn't suffer from fragmentation.
BTW: The heap space is only part of the memory used, you need memory for shared libraries, direct memory, GUI components etc.
It seems you don't have 3G of physical mememory available. Here is an interesting article on Java heap size settings errors. Java heap size setting errors
I have a system which cannot provide more than 1.5 Gb for Java process. Thus i need an exact way to specify java process settings, including all memory kinds inside java and possible fork.
One specific java process and system to illustrate my problem:
My current environment is java 1.6.0_18 under Ubuntu Linux 9.10.
I start large java server process with following JVM Options:
"-Xms512m -Xmx1024m -XX:PermSize=256m -XX:MaxPermSize=512m"
Now, "top" command reports that the process uses 1.6gb memory...
Questions:
1 - how the maximal space used by java process is calculated? Please provide exact formula if possible.
( Smth. Like: max.heap + max.perm + stack + jvm space = maximal space )
2 - what is the infamous fork behavior under linux in my case? Will the forked JVM occupy extra 1.6 gb (resulting in total 3.2 Gb of used memory)?
3 - Which options must be used to absolutely ensure that no more than 1.5gb is used at any time?
thank you
#rancidfishbreath: "ulimit" will ensure that java cannot take more than specified amount of memory. My purpose is to ensure that java doesn't ever try to do that.
top reports 1.6GB because PermSize is ON TOP of the heap-size maximum heap size. In your case you set MaxPermSize to 512m and Xmx to 1024m. This amounts to 1536m. Just like in other languages, an absolutely precise number can not be calculated unless you know precisely how many threads are started, how many file handles are used, etc. The stack size per thread depends on the OS and JDK version, in your case its 1024k (if it is a 64bit machine). So if you have 10 threads you use 10240k extra as the stack is not allocated from the heap (Xmx). Most applications that behave nicely work perfectly when setting a lower stack and MaxPermSize. Try to set the ThreadStackSize to 128k and if you get a StackOverflowError (i.e. if you do lots of deep recursions) you can increase it in small steps until the problem disappears.
So my answer is essentially that you can not control it down to the MB how much the Java process will use, but you come fairly close by setting i.e. -Xmx1024m -XX:MaxPermSize=384m and -XX:ThreadStackSize=128k -XX:+UseCompressedOops. Even if you have lots of threads you will still have plenty of headroom until you reach 1.5GB. The UseCompressedOops tells the VM to use narrow pointers even when running on a 64bit JVM, thus saving some memory.
At high level JVM address space is divided in three main parts:
kernel space: ~1GB, also depends on platform, windows its more than 1GB
Java Heap: Java heap specified by user using the -Xmx, -XX:MaxPermSize, etc...
Rest of virtual address space goes to native usage of JVM, to accomodate the malloc/calloc done by JVM, native threads stack: thread respective the java threads and addition JVM native threads for GC, etc...
So you have (4GB - kernel space 1-1.25GB) ~2.75GB to play with,so you can set your java/native heap accordingly. But generally we should keep atleast 500MB for JVM native heap else there is a chances that you get native OOM. So we need to do a trade off here based on your application's java heap utilization.