Tag: java

Sun/Oracle Java Default Values

/opt/java/jdk1.6.0_21/bin/java -XX:+PrintFlagsFinal -version [Global flags] uintx AdaptivePermSizeWeight               = 20               {product} uintx AdaptiveSizeDecrementScaleFactor     = 4                {product} uintx AdaptiveSizeMajorGCDecayTimeScale    = 10               {product} uintx AdaptiveSizePausePolicy              = 0                {product} uintx AdaptiveSizePolicyCollectionCostMargin  = 50               {product} uintx AdaptiveSizePolicyInitializingSteps  = 20               {product} uintx AdaptiveSizePolicyOutputInterval     = 0                {product}…

Getting JVM config

Use jmap to get a running JVM configuration For example: <path2java>/bin/jmap -heap <pid> JVM version is 17.0-b16 using parallel threads in the new generation. using thread-local object allocation. Concurrent Mark-Sweep GC Heap Configuration:    MinHeapFreeRatio = 40    MaxHeapFreeRatio =…

JVM Heap and Thread Dumps

Thread dump from a running JVM to a file, the -J-64 is 64bit JVMs: jmap -J-d64 -dump:format=b,file=<file> <pid> Thread dump from a running JVM to stderr of the process: kill -3 <pid> Heap dump from a running JVM, the -J-64…

Java and DNS lookups

Java by default caches successful DNS lookup forever. Turning changing this will have performance impact befauce of DNS lookups and there are security concerns. If you are using load balancing that relies on DNS this will need to be changed.…