(Java is not bundled into 'clean' installations of Lion, but can be added later.) Java was bundled into Apple's Mac OS X 10.6 Snow Leopard by default, and kept on if a Mac user upgraded his machine from Snow Leopard to Mac OS X 10.7 Lion.

Explaining has a long history of security vulnerabilities, which are now coming to the public's attention because of the widespread infection of Macs in late March by the Flashback, also called Flashfake, malware family.

StackOverflow : What is ‘PermSize’ in Java?.

Ergonomics in the 5.0 Java Virtual Machine.

Oracle Presenting the Permanent Generation.

Just some find out and sharing, do let me know your comment. The best practice is found out your memory detail, then fine tune the values accordingly. Conclusionįinally, the default values of heap memory, perm gem and stack size is different from each JVMs, do not expect JVM will assign the optimal values for your Java application. This -XX:+PrintCommandLineFlags is used to print out the values that modified by VM only (indicated by this := symbol). Uintx InitialHeapSize := 64781184 | grep HeapSizeĪ. $ java -XX:+PrintFlagsFinal -version | grep -iE 'HeapSize|PermSize|ThreadStackSize' OS : Ubuntu 13 (64 bits) (Under VirtualBox) If a project has a lot of threads processing, try reduce this stack size to avoid running out of memory. $ java -XX:PermSize=64m -XX:MaxPermSize=128m JavaApp

XX:MaxPermSize - Set the maximum PermGen Size.

If a large code-base project is loaded, the insufficient Perm Gen size will cause the popular : PermGen. Place to store your loaded class definition and metadata. For a heavy Java process, insufficient Heap size will cause the popular : Java heap space. Place to store objects created by your Java application, this is where Garbage Collection takes place, the memory used by your Java application. Java Memory OverviewĪ quick review of Java memory structure : However, above algorithms are just for reference, it may vary in different VM. Maximum heap size of 1/4 of physical memory up to 1Gbyte Initial heap size of 1/64 of physical memory up to 1Gbyte

In Java, the default and maximum heap size are allocated based on this – ergonomics algorithm. In this article, we will show you how to use the -XX:+PrintFlagsFinal to find out your heap size detail.

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