Dileep Kumar's Weblog

I have been working on some simplification for the WebSphere App Server V6.1 performance tuning on Solaris 10 platform and it came to my attention that instead of playing with too many flags there is only one flag should be more than good enough to give the boost needed for performance. However this may not apply to all the work load but I would rather try and determine that and start overriding some of the defaults:

Previously the tuning knobs of interest used to be like following:

• initialHeapSize= eg. 2048
  
• maximumHeapSize= eg. 2048
  
• -server
  
• -Xmn1024m At least 50% of the heap size; more may be better
  
• -XX:-ScavengeBeforeFullGC
  
• -XX:MaxTenuringThreshold=
  
• -XX:+UseParallelGC
  
• -XX:ParallelGCThreads= either equal to number of cpu or on multi core systems set it to somewhere between .5-1xNumber of cores.
  
• -XX:+AggressiveHeap
  
• -XX:PermSize=
  
• -XX:+UseParallelOldGC
  

All of this can be reduced to just couple of flags and it will give more throughput than this one:
So the new reccomendations are:

• initialHeapSize= eg. 2048
  
• maximumHeapSize= eg. 2048
  
• -server May not be needed in most cases
  
• -XX:+AggressiveOpts -XX:+UnlockDiagnosticVMOptions -XX:-EliminateZeroing
  

This will take care of JVM tuning and you should spend time setting the websphere thread pools right.
Let me know if you find it other way...