Every once in a while I run into someone that has a JVM that is running back to back collections and yet the heap is still almost full after each attempt! When they discover that their problem is related to the JVM not having enough memory they often ask the question, why didn't the JVM throw an OutOfMemoryError? After all my application is not making any forward progress and the reason is Java...
on Jan 8, 2014
Just recently I was engaged to assist with an application that wasn’t behaving. The application, running in a 1.7.0_45 JVM, relied heavily on a 3rd party SAAS framework. That vendor provided my client with a list of 26 different JVM flags that should be set. When faced with this long list of flags I couldn’t resist asking why all the flags and why these flags. After all there are more than 700...
on Dec 11, 2013
More than a few days ago a friend pinged me complaining that recent Eclipse release was quite sluggish. Since she had taken my performance tuning seminar she knew exactly how to get and read a GC log but as we all do, she was looking for a second opinion. After looking at the log for a minute it because quite apparent that the default configuration left the IDE starved for memory. After a bit...
on Oct 21, 2012
While I don't normally blog about the exiting world of JVM command line options, this new 7.0 option, which allows you to rotate to a new GC log file, was just so exciting... err... not so widely published that I decided to share. Of course these options only apply when you've used the -Xloggc: option. The settings are;
UseGCLogFileRotation, default value: false
NumberOfGCLogsFiles, default value...
on Aug 20, 2012
Today I decided it was past time to reorganize the slides in the performance testing section of the course. I added a number of new diagrams and charts to help organize the materials and then I went back and started to review some of the definitions that I was using. First up was the question; what is performance testing and how is it related to load testing.
I must confess that I derived a...
on Jan 12, 2012
I mentioned the idea to use Wordle as an execution profiler while presenting the profiling section of my performance tuning course in Paris last December. The idea was seeded by presentation that Neal Ford did a few years ago in which he used Wordle to expose the vocabulary of a Java application. Neal took a pile of source code and fed it into Wordle. The result was a word cloud that visualized...
on Jan 9, 2012
It’s after JavaONE and as promised, here is the answer to the performance puzzler with a stack trace. But first a word about JavaONE. The physical layout was the same as last year and as a result, JavaONE suffered from some of the same problems as last year. This year Oracle took a lot of advice from an advisory committee and the result was the conference made very good use of the poor...
on Oct 10, 2011