Showing posts with label java. Show all posts
Showing posts with label java. Show all posts

Thursday, 5 June 2014

Setting Up JVM Heap Size In JBoss OpenShift Origin

Openshift is an awesome technology and have fell in love with it recently. In this post, I will talk about how we can set JVM Heap Size for your application using Jboss cartridge.

If you look into the content of the standalone.conf located at $OPENSHIFT_JBOSSEAP_DIR/bin, you can see that JVM_HEAP_RATIO is set to 0.5 if it is not already set.

if [ -z "$JVM_HEAP_RATIO" ]; then

And, later this ratio is used to calculate the max_heap so as to inject the maximum heap size in jboss java process. You can see how gear memory size is used to calculate the value of heap size. This is the very reason why the default installation allocates half of total gear memory size.

max_heap=$( echo "$max_memory_mb * $JVM_HEAP_RATIO" | bc | awk '{print int($1+0.5)}')

OpenShift keeps its number of environment variables inside /var/lib/openshift/OPENSHIFT_GEAR_UUID/.env so what I did was SSH to my OO node and run the command below (you should replace your gear's UUID):

$ echo -n 0.7 > /var/lib/openshift/52e8d31bfa7c355caf000039/.env/JVM_HEAP_RATIO

Alternatively, rhc set-env JVM_HEAP_RATIO=0.7 -a appName should also work but I have not tried it.


Thursday, 27 June 2013

Manual Sun Java Installation In Linux

Be it be multiple installations of java or be it be custom server, you might run into the necessity of manually installing java. This tutorial will provide step by step commands for installing java manually in linux.

Though the process was done on CentOS, it should work for most linux systems with or without slightest modifications. The process below installs Sun Java and configures Sun Java to be the default java to be used. Below are the steps I took to install and configure java in my system:

$ cd /opt/java
$ wget
$ tar xvfz jdk-6u45-linux-i586.tar.gz
$ echo 'export JAVA_HOME=/opt/java/jdk1.6.0_45' > /etc/profile.d/
$ echo 'export PATH=$JAVA_HOME/bin:$PATH' >> /etc/profile.d/
$ alternatives --install /usr/bin/java java /opt/java/jdk1.6.0_45/bin/java 2
$ java -version
java version "1.6.0_45"
Java(TM) SE Runtime Environment (build 1.6.0_45-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)

If you wish to reconfigure the default java, you can run alternatives as below & choose the appropriate option:

$ alternatives --config java
I hope this helps :)


Sunday, 12 August 2012

Rootbeer - High Performance GPU Computing in JAVA

Good news for JAVA guys that the high performance GPU compiler has been released that aims to bring high performance GPU computing to the Java Programming Language with the minimal effort from the developer.

Rootbeer is more advanced than CUDA or OpenCL Java Language Bindings. With bindings the developer must serialize complex graphs of objects into arrays of primitive types. With Rootbeer this is done automatically. Also with language bindings, the developer must write the GPU kernel in CUDA or OpenCL. With Rootbeer a static analysis of the Java Bytecode is done (using Soot) and CUDA code is automatically generated.

Rootbeer was created using Test Driven Development and testing is essentially important in Rootbeer. Rootbeer is 20k lines of product for and 7k of test code and all tests pass on both Windows and Linux. The Rootbeer test case suite covers every aspect of the Java Programming language except:
1. native methods
2. reflection
3. dynamic method invocation
4. sleeping while inside a monitor.

This means that all of the familar Java code you have been writing can be executed on the GPU.

GitHub of Rootbeer