Pete Freitag Pete Freitag

Have you tuned your JVM on ColdFusion MX yet?

Updated on December 06, 2023
By Pete Freitag

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 completely on Macromedia to make performance optimizations, we can use different JVM's and lots of different JVM settings to improve the performance and scalability 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 compilation, etc
  • BEA and Red Hat Partner to Deliver Unparalleled Java Performance For Enterprise-Class Linux (,1072,47280,00.html)
  • 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 supposed to work well on multi-processor 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

Update: I have removed most of these links because they no longer work. You should take a look at this article I wrote: Performance Tuning Garbage Collection in Java

jvm java cf

Have you tuned your JVM on ColdFusion MX yet? was first published on September 25, 2002.

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Your links here are pretty helpful. I just recently went to new york to help a client solve problems related to the dreaded Java.lang.OutOfMemory error which is in large part to lack of good degault settings in the Jrun.xml for the scheduler (and somewhat for the proxy) service. Alot of people who are getting these errors mistakenly think its only a JVM issue but its a jrun.xml settings issue but tuning the JVM can really increase performance, reduce the out of memory errors and in general make more people happy. Some time this weekend Ill blog all my results as well as my general rules and ideas on JVM tuning for CFMX.
by robi on 08/26/2004 at 3:24:39 PM UTC
I am having several issues that appear as you stated Robi. They are JVM errors as the logs state, relating to memory. I was interested in reading your blog, but the link isn't working for me. Hopefully you will get this message so I may be enlightened. I'm running the latest 6.1 package of CFMX, and this thing kills a server at least 4 times a day now. Any help would be appreciated. I may start testing a new jvm if you don't get this!

by Pete on 09/21/2005 at 9:03:01 PM UTC
BTW, I'm a different Pete.. Should have stated so! Insightful article Pete #1.

by Pete (M) on 09/21/2005 at 9:04:10 PM UTC
Good information! I am looking to dig into CFMX threads, so that I can see specific code executing. I know that we can issue dumps of a stack trace; however, I am looking for something a bit more easy to implement in a production environment. It seems to me, that I should be able to see CFMX programs run in real time. I can see the individual threads, but not the underlying code that is executing. We are running CFMX 6.1 and have been for almost four years without any problems at all. However, lately we see high CPU usage with threads stacking up. We can communicate with all Databases, but the threads still stack during peak load time. Any thoughts on a tool or existing Java methods I can use to acquire more information?
by borg on 01/28/2008 at 9:23:57 PM UTC