You need to do proper GC tuning before doing the migration, otherwise, your application can experience several seconds to few minutes pause time. When you increase heap size, your GC pause times will start to go high automatically, because now there is more garbage in the memory to clear up. The primary reason to migrate from 32-bit JVM to 64-bit JVM is to attain large heap size (i.e. What are the things to consider when migrating from 32-bit JVM to 64-bit JVM? These extra registers increase performance to the point where there is often no performance loss at all when comparing 32 to 64-bit execution speed. The good news is that with AMD64 and EM64T platforms running in 64-bit mode, the Java VM gets some additional registers which it can use to generate more efficient native instruction sequences. The loading of this extra data has an impact on memory usage which translates to slightly slower execution depending on how many pointers get loaded during the execution of your Java program. This is due to the fact that every native pointer in the system takes up 8 bytes instead of 4. How can 64-bit JVM performance be slower than 32-bit JVM? It means your application’s maximum addressable memory size is close to infinite. If you are running your application on a 64-bit JVM, maximum addressable memory space is 2^64 (i.e. This table summarizes maximum heap size that you can set on 32-bit JVM:
Due to various additional constraints (such as available swap, kernel address space usage, memory fragmentation, and VM overhead), in practice, the limit is much lower. It means the maximum memory size of your Java process can’t be more than 4GB. In 32-bit JVM maximum, addressable memory space is only 2^32 (i.e.~4gb). On AMD64 and EM64T platforms this difference ranges from 0-15% depending on the amount of pointer accessing your application performs.” If there is a performance hit, why would anyone use 64-bit JVM? The performance difference comparing an application running on a 64-bit platform versus a 32-bit platform on SPARC is on the order of 10-20% degradation when you move to a 64-bit VM. “Generally, the benefits of being able to address larger amounts of memory come with a small performance loss in 64-bit VMs versus running the same application on a 32-bit VM. Below is the excerpt from Oracle JDK documentation regarding 64-bit JVM performance: 64-bit JVM can have a small performance degradation compared to 32-bit JVM. Most of us think 64-bit is bigger than 32-bit, and that 64-bit JVM performance will be better than 32-bit JVM performance. Does 64-bit JVM perform better than 32-bit JVM? The subtle difference between 32-bit JVM and 64-bit JVM wouldn’t make much difference to your application. If you aren’t building a performance-critical application, you don’t have to understand the difference. We thought we will try to clarify them through this question-and-answer article Do I need to understand the difference between 32-bit JVM and 64-bit JVM? # /opt/java7/bin/java -version java version "1.7.0.07" Java(TM) SE Runtime Environment (build 1.7.0.07-jinteg_2013_07_11_08_03-b00) Java HotSpot(TM) Server VM (build 23.21-b01-jre1.7.0.There are a few distinct differences and subtle nuances between 32-bit JVM and 64-bit JVM. #file /opt/java6/bin/java /opt/java6/bin/java: PA-RISC2.0 executable dynamically linked -not stripped
How can I confirm teh version installed is 32 bit or 64bit? I checked older post and found out there is no separate JDK fro 32 bit and 64 bit but how can I confirm this.Īttaching soem o/p from server for reference. As per oracle support they are telling teh java installed is 32 bit. Now we are in the phase of installing Oracle Middleware and facing issues in installation. I am using HP-UX 11.31 March 2013 on Itanium Blade 860C i2 server. HPE Blog, Austria, Germany & Switzerland.