Thursday, March 6, 2008

Talk on x86 Memory Model

Rick Hudson gave a talk at Google about the new official memory model for the Intel x86 platform. Good stuff, for memory model geeks.

Wednesday, March 5, 2008

Java Performance Talk

Paul Tyma and I gave a talk at SD West today on Java Performance Myths.

The big takeaway was this: Most of the things you think you know about Java performance are really hard to quantify. Write the best code you can. Profile it to find the bottlenecks. Remove the bottlenecks. Rinse and repeat.

A couple of other takeaway points here:
  • Don't forget to upgrade every so often. JDK6, for example, runs code compiled for JDK4 just fine, and you get a big performance boost. For free.

  • Memory allocation is pretty cheap. Know that there are three garbage collectors, and know which one is best, when. Read the Java memory management white paper.

  • Hotspot can do lots of things to optimize your locks, but it often doesn't. Having said that, the bottlenecks in concurrent code usually have to do with contention, not synchronization overhead. Use low contention data structures like ConcurrentHashMap to avoid contention, but don't try to get clever with locking.

  • Contrary to popular belief, thread-per-request synchronous servers are often faster than selector-based asynchronous servers.

The Java Performance Myths slides are here.

Hotspot Garbage Collection

Thought of the Day: The production version of Hotspot has 211 command line options for garbage collection. Getting the right combination of options is hard.