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Mission Impossible with Kirk Pepperdine

Last Tuesday Kirk Pepperdine gave a talk at Warszawa Java User Group. Kirk is a Real Guru in the Java world so I was truly excited to meet him. He has been working in high performance and distributed computing for nearly 20 years. What is more, in 2006 Kirk was recognized by Sun Microsystems as a Java Champion recipient for his contributions to the Java community.

“Performance Tuning with Cheap Drink and Poor Tools” was the topic of the session. At the beginning participants got a cheap food (pizza) and a cheap drink (coke) – so everybody was in high spirits :) You can expect everything when you attend a JUG meeting. Sometimes people present something you actually got acquainted with very well, sometimes you don’t know the subject, but Wikipedia, Google and Eclipse would give you the same answers without leaving your home. Some sessions are, however, sensational – and Kirk’s talk was really that case!

At first, Kirk put emphasis on the fact that there is no taxonomy regarding performance tuning. The main problem is that very often developers do not realize that the process of giving a performance boost to an application is much different than the development itself. Kirk made a joke that many companies tune their application in accordance with the following rule:

“We don’t know where we are going, but we are having a great time” .

According to the speaker, issues concerning performance should be take into consideration at every stage of the project life-cycle. Could we disagree with that? I don’t think so, but why it is neglected most of the time…?

Later, Kirk presented a sample application which encompassed the most common performance bottlenecks. The audience was supposed to tune it on the spot. It was really funny as this simple exercise showed the main problem right away! Developers are used to work with the code – we can even say that we love the code :) So, what do we actually do to solve potential performance problems? – we look into the code! According to Kirk it is the last thing that should be done. However, to cut the long story short, here are some general rules presented by Kirk:

  • When is the performance bad? – When users do complain!
  • Everything matters – tune application in exactly the same hardware/software environment as the production environment.
  • DON’T LOOK INTO THE CODE unless you really know where you wanna look.
  • Find the DC (dominating consumer): application, jvm, os, hardware.
  • If CPU kernel time is higher than 10% – application is the DC.
  • Use poor tools – such as: jps, jstack, jvisualvm – to locate the piece of code that is responsible for the degradation of performance. THEN look into the code to modify it.
  • Using a profiler is the last step
  • Don’t shoot wild – don’t do anything blindfold – making your code look beautiful won’t help!

Do you agree with that? YES, YES, YES ;)

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