Have you tuned your JVM on ColdFusion MX yet?

ColdFusion's move to java gives developers and system administrators a wealth of performance tuning options. This is due to the fact that the runtime for ColdFusion is now pluggable (the JVM), we don't have to rely completly on Macromedia to make performance optomizations, we can use different JVM's and lots of different JVM settings to improve the performance and scalibility of our ColdFusion Applications. This is a topic I haven't seen much discussion about yet, and I'm not sure why.

What JVM should I use?

You have lots of choices, IBM, Sun and BEA all make JVM's, each will perform differently. Which is the fastest? I couldn't tell you, it will depend on your server platform, and your application. Sun being the creator of Java, has the most popular JVM, but if you are really concerned about performance you should test with each vendor's JVM.
Here are some articles that may help make your decision (in no particular order)

• Java 1.4 Performance Guide - If your using Sun 1.3 you should probably think about upgrading to 1.4, due to huge increases in JNI performance (if you use COM, Registry, Verity you should see a big boost), Increased threading performance, 35% servlet performance increase (CFM pages are run as servlets in CFMX), byte code to native code compliation, etc
• BEA and Red Hat Partner to Deliver Unparalleled Java Performance For Enterprise-Class Linux
• The Volano Report - a benchmark, this report is 9 months old.
• Spec JVM98 Benchmark - reports are kind of old, but you can buy the benchmark software and run your own tests on your system.

Tuning Your JVM There are lots of things you can do to tune the JVM, typically there are memory settings, threading settings, and garbage collection settings. For memory settings make sure you Max heap is big enough, also set the initial heap size to be equal to the max heap size, this way all memory is allocate when the server starts up, rather than when it needs it (during a request, allocating memory is slow). Look for a file called Xusage that comes with your JVM this usually shows some of the options that you can set, also look in your JVM docs for more info. You can tune these settings just like you tune your web server or other web applications. Sun Performance tuning links

• Java Performance FAQ
• Java Performance Docs (sun) - lots of good stuff here
• Java Platform Performance Strategies Aad Tactics - buy the book or get it free online
• Java HotSpot VM Options - docs on all the jvm settings for sun jvm's
• Tuning Garbage Collection - currently this doc is for 1.3.1, the sun jvm 1.4.1 includes an additional garbage collector, a concurrent gc which is suspossed to work well on multi-processer servers.
• Tuning Threads - this deals only with Solaris because you can choose different threading models on Solaris.
• Big Heaps, and Intimate Shared Memory (ISM) Big Heaps stuff applies to all platforms, the ISM is solaris only.

I haven't had the time to do any JVM testing on ColdFusion MX yet, but if you have I'd love to hear about your experiences email me pete@cfdev.com.