Useful Java flags and techniques
--------------------------------

FLAGS

-verbosegc : Outputs garbage collection information from the running JVM

-Xrunhprof : Provides runtime JVM statistics (heap, cpu, etc...)

 example
  -Xrunhprof:file=log.txt,thread=y,depth=3
  
 syntax
  -Xrunhprof[:help]|[:option=value,option2=value2, ...]
  
 parameters
  OptionName and Value   Description   Default
  ---------------------  -----------   -------
  heap=dump|sites|all   heap profiling   all
  cpu=samples|old   CPU usage   off
  format=a|b    ascii or binary output  a
  file=    write data to file  java.hprof
  net=:   send data over a socket write to file
  depth=    stack trace   depth 4
  cutoff=    output cutoff point  0.0001
  lineno=y|n    line number in traces?  y
  thread=y|n    thread in traces?  n
  doe=y|n    dump on exit?   y

--XX:ThreadStackSize=512 : Specify the size of stack for each new Java thread.

-XX:+AggressiveHeap : This option instructs the JVM to push memory use to the
 limit: the overall heap is 3900MB, the new generation is 3072MB, the allocation area
 of each thread is 256KB, and the collection policy defers as long as possible before
 collecting.

-Xms3g -Xmx3g : Sets the heap minimum and maximum size to 3GB (use 'm' for megabytes)

-server : Use optimizing JIT compiler

-XX:+UseConcMarkSweepGC : Use concurrent garbage collector

-XX:+UseParallelGC : Use parallel garbage collector

-Xint : Interpret only, no JIT

-XX:+DisableExplicitGC : Disable calls to System.gc(), JVM still performs garbage collection when necessary

-m