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I need to run a Java memory intensive application that uses more than 2GB, but I am having problems to increase the heap maximum size. So far, I have tried the following approaches:
Setting the -Xmx parameter, e.g. -Xmx3000m. This approaches fails at the creation of the JVM. From what I've googled, it looks like that -Xmx must be less than 2GB.
Using the -XX:+AggressiveHeap option. When I try this approach I get an 'Not enough memory' error that tells that the heap size is 1273.4 MB, even though my computer has 8GB of memory.
Is there another approach that I can try to increase the maximum heap size of the JVM? Here's a summary of the computer specs:
java version "1.6.0_18" Java(TM) SE Runtime Environment (build 1.6.0_18-b07) Java HotSpot(TM) Client VM (build 16.0-b13, mixed mode, sharing)
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You can improve performance by increasing your heap size or using a different garbage collector. In general, for long-running server applications, use the J2SE throughput collector on machines with multiple processors (-XX:+AggressiveHeap) and as large a heap as you can fit in the free memory of your machine.
The theoretical limit is 2^64 bytes, which is 16 exabytes (1 exabyte = 1024 petabytes, 1 petabyte = 1024 terabytes). However, most OS's can't handle that. For instance, Linux can only support 64 terabytes of data. Note: We don't recommend you exceed 2 GB of in use JVM heap.
Larger heap size will cause less frequent, but bigger and more disruptive garbage collection if using the traditional oracle garbage collection algorithm. So bigger is not better. The exact behavior will depend on the JVM implementation.
When you are using JVM in 32-bit mode, the maximum heap size that can be allocated is 1280 MB. So, if you want to go beyond that, you need to invoke JVM in 64-mode.
You can use following:
$ java -d64 -Xms512m -Xmx4g HelloWorld where,
You can tune in -Xms and -Xmx as per you requirements (YMMV)
A very good resource on JVM performance tuning, which might want to look into: http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html
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