This new (free) WebSphere Application Server Performance Cookbook covers performance tuning for WebSphere Application Server, although there is also a very strong focus on Java, Operating Systems, and theory which can be applied to other products and environments. This is an amazing piece of work. IBM has a history of publishing performance tuning guidelines for its products (MQ, Message Broker, etc.), but this cookbook is by far the best. It really does cover way more than just the WAS and Liberty Profile products. About half of the cookbook is about OS, Java, network tuning and tools. If you are tuning JBoss or Tomcat – you can use that half of the book (feel free to send a donation to IBM for providing this service).