... Java so fast it blows women's cloths off!

The question I am trying to answer is what does it take to get Java to perform so fast it blows women's cloths off. The goal is not to understand what is fast - but simply to look at techniques which are faster than anything else available.

1. Never use java.util (collections). They generate tremendous amount of garbage and are slow.

• Trove
• Colt
• If you don't believe me - http://b010.blogspot.nl/2009/05/speed-comparison-of-1-javas-built-in.html   

2. Avoid garbage collection

• http://docs.oracle.com/cd/E19900-01/819-4742/abeik/index.html - No minor GC collections until Eden fills up - so make your Eden larger. (-XX:MaxNewSize)
• http://java-performance.info/overview-of-memory-saving-techniques-java/

 3. Reuse strings.

• http://java-performance.info/string-intern-in-java-6-7-8/
• https://github.com/OpenHFT/Java-Lang/blob/master/lang/src/main/java/net/openhft/lang/pool/StringInterner.java - very quick way to do on heap intern

3. Async Logging - i.e. don't spend all your time writing logs

• http://logging.apache.org/log4j/2.x/manual/async.html
• https://github.com/OpenHFT/Java-Chronicle - record everything for high-frequency-trading (read fast enough to blow women's cloths off)

4. Don't use the Heap - i.e. No heap = no GC.

• https://github.com/OpenHFT/HugeCollections - off heap storage
• https://github.com/OpenHFT/Java-Lang

5.  Know what the heck your system is doing. Maybe it's the machine and not your crappy-code?

• http://www.azulsystems.com/jhiccup - unexplained processing pauses
• http://dtrace.org/blogs/brendan/2013/06/08/linux-performance-analysis-and-tools/ - tools to monitor Linux
• http://www.joyent.com/blog/the-new-systems-performance - some more tools

6. Use a ring instead of a queue / thread message passing

• http://lmax-exchange.github.io/disruptor/ - inter thread message passing.

7. Maybe the problem isn't with your code at all - but with the watch you use?

• https://github.com/hajile/microclock - library implementing RDTSC (let's count the CPU clock cycles)
• http://www.strchr.com/performance_measurements_with_rdtsc
• https://github.com/giltene/HdrHistogram - more precise measurements

8. Keep your methods short and sweet - helps with hotspot

•  Write code that is easy for the optimizer - https://wikis.oracle.com/display/HotSpotInternals/PerformanceTechniques

9. Try some exotic features

• https://github.com/OpenHFT/Java-Thread-Affinity - Thread affinity
• http://www.docjar.com/docs/api/sun/misc/Unsafe.html - a magical class in the JDK, which does everything a magnitude faster, but don't use it without protection. It's unsafe. 
• http://architects.dzone.com/articles/getting-cc-performance-java - serialization using Unsafe

 10. CAS / optimistic locking / lock free

• http://java.dzone.com/articles/lock-based-vs-lock-free - no locks is a lot faster than with locks (no shit).
• http://www.infoq.com/articles/memory_barriers_jvm_concurrency - use volatile but only at your own risk
• 
  

DemiGods in this space - 

• http://mechanical-sympathy.blogspot.com/ - LMAX Tech Architect Guy
• http://vanillajava.blogspot.com/ - HFT Java Guy