Develop Reference

Asking for more memory than possible in java

I am running a java application with -Xms120g -Xmx120g on Mac laptop with 16GB of memory. What I saw was that the application was running and it consumed uptil now 36 GB of memory. I am guessing the Mac OS is using virtual memory to meet the demands of the application. However, I was wondering if I set a value of -Xms to something that the machine can't possibly provide will the application crash immediately or will it run and then only crash when it actually uses all the memory that the system can provide.

Found an explaination here:
Why am I able to set -Xmx to a value greater than physical and virtual memory on the machine on both Windows and Solaris?
So it works to excede the available virtual memory but eventually the metadata needed to handle the heap will need to much memory and it crashes.

JVM 64 is using a maximum of 2GB on Windows Server 2012 on Azure

I'm using a Windows 2012 server with 7GB of ram that is on Azure.
I have installed 64 bit java on the machine.
When running the jvm, I have set the maximum heapsize to 4GB via the argument
-Xmx6g
However, when I'm running my jar, it encounter a java OutOfMemory exception. I have checked the task manager while it is running and it shows that memory used for the process peaks at around 2GB and never goes past that. This despite me setting heapsize to 6GB.
On my local PC, where I am using a Windows 7 machine with 8GM of ram, I do not encounter this issue.
I used the following commands in my java app
System.out.println(System.getProperty("sun.arch.data.model"));
System.out.println("Max Memory: " + Runtime.getRuntime().maxMemory());
And it gives me the following:
Windows Server 2012
64
1670381568
Local PC
64
6681001984
Why is the Windows Server not allocating the full amount of memory to the JVM? Is there any setting that I am missing?

This is really dumb and stupid of me but I figured out the cause of it.
I had placed the memory arguments at the end of my whole command line when I needed to put it just after the java command.
i.e. Instead of
java -jar "myapp.jar" "myArgs" -Xmx6g
I should have used
java -Xmx6g -jar "myapp.jar" "myArgs"

Either the -Xmx parameter is not being considered or the process is not allowed to get more RAM from the OS.
My suggestions:
Try using -Xmx4096m instead.
Not familiar with Azure but I've read that there are ways to limit memory per process/shell. Could that be an issue here? (Ref: http://msdn.microsoft.com/en-us/library/aa384372(VS.85).aspx , taken from http://social.technet.microsoft.com/Forums/en-US/2ba92acf-e1b9-4a3e-8ae7-f8ac31723959/problem-with-running-java-application-into-a-win-vm-of-azure-by-using-powershell-remoting?forum=WAVirtualMachinesforWindows )
Finally, are the Java versions exactly the same on both places? (I mean, do you need a special Java JRE on Azure?)
Note: I would've used a comment since this is not actually a solution but I don't have the points yet. I apologize if this is not the correct way to contribute.

setting up 64bit windows 7 for large JRE7 heap size

I have been trying to run java with 4G max and min heap size on a 64bit win 7 machine but when I check task manager I only see about 2G for java.exe. I read there are windows restrictions as well. How do I set up windows 7 and jre7 x64 so that I can run jave with 4G heap size?
Thanks.

What parameters are you using?
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html
For example related to your case:
-Xms : sets initial Java heap size
-Xmx : sets maximum Java heap size
If you are using the -Xmx parameter then you will see 4G in your task manager, ONLY IF your application really needs it. On the other hand if your are using the -Xms parameter (in that case you also need to need to set -Xmx parameter at an equal or larger value) then you should expect to see that value on the task manager. So, only if you set -Xms4096M and -Xmx4096M and the JVM fails to start then you have an issue. If it starts normally then you do not have a problem.
Also regardless of the RAM you are having (not in your case since we are only talking 4G) even Windows 7 (64bit) have different limits according to their edition.
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778%28v=vs.85%29.aspx#physical_memory_limits_windows_7

Couple of times in my past experience, I observed that 64-bit OS can also have 32-bit JVM and it leads to the confusion.
Apart from this, I don't think you will be able to allocate full 4 GB space to JVM, there are other programs which consumes the memory also.
You can think of allocating 4 GB only if you are running on >6 GB machine.

"Could not create the Java Virtual Machine" when increasing the -Xmx

The eclipse on my work computer was working with VM argument -Xms40m and -Xmx512m and it is really slow and freezes a lot, I wanted to increase it to -Xmx1024m, but every time I did so I got the error "Could not create the Java Virtual Machine".
The computer has 3.5GB RAM, WIN XP (32-bit), Java 1.6_18
What could be the reason? Is it related to other arguments?
UPDATE:
I changed the -vm argument so it will use the jvm.dll that comes with the jrockit JDK and I was able to increase the max heap size to 1024m.
Also, on my home computer (WIN 7, 32-bit, 2GB RAM, java 1.7.0_21-b11), I was able to increase it 1024m as well.

The maximum amount of memory available on Windows 32-bit processes is (generally speaking) 2GB. That includes everything for your JVM, not only the application heap. People report various numbers for the maximum heap that can use for a 32-bit JVM, but 1200m is a common figure. It seems to be lower for you. Best would be to switch to the 64-bit JVM, if you can.
Other questions:
How much memory can a 32 bit process access on a 64 bit operating system?
Java maximum memory on Windows XP

more memory allocation in java program

I use ubuntu 10.04 LTS 64bit and my system has 4 GB RAM.
I run a java program that need more than 1.1GB memory but the operating system does not allow my program to get more than 1.1GB while only 2.1GB of RAM is used and 1.9GB are free, what is the problem? (This problem is not just for this program, I run another program and has same problem.)
what should I do?

Looks like you are running a java application. Make sure to
Run a 64 bit JVM, if you need more than about 4GB memory. For this to work, you shold have a 64 bit OS
Increase the max heap size by the JVM switch
-Xms <initial size> -Xmx <max size>

Sounds like you programs are compiled as 32bit programs despite that you are running on a 64bit configuration.