thanks for the feedback. On 8/18/05, Jonathan Oexner <[EMAIL PROTECTED]> wrote: > Hi all, > I'm just getting started with webapp performance testing with JMeter, > and I noticed the bug mentioned in the thread 'Possible bug in monitor > results listener' from late last year, still present in release 2.0.3 > . I downloaded the nightly 2-1.20050812, only to find that the bug > "fix" in CVS is still a little off. The memory usage that most people > want to see (IMHO) is: > > current usage / maximum available > > as opposed to: > > current usage / current heap size > > > They don't really care what the JVM is doing to the current heap size; > they just want to know the absolute usage, and how close the are to an > OutOfMemoryError. Additionally, since the *currently allocated* heap > size will change whenever the JVM decides to change it, using it for > the denominator makes it very hard to get an idea of the actual usage. > I'm much too lazy to submit an actual patch, but in > $JMETER_HOME/src/monitor/components/org/apache/jmeter/monitor/util/Stats.java > , I changed the two methods below, and the results make a whole lot > more sense this way.
In practice this is not true. In most cases, a server will crash before it reaches the max heap size. I tested tomcat about 2 dozen times with a wide variety of loads. I actually started with the assumption that max heap was better, but after I ran some tests, it became apparent that wasn't true. if you were to profile tomcat with verbose GC you would see that often an application runs out of memory because the JVM is unable to resize the heap fast enough. this typically happens with a sudden traffic spike occurs. Under steady constant or semi-constant load, current usage / current heap is also more accurate. Say for example I set my max heap to 512Mb. If constant load uses 200, using the max heap won't tell me much. In fact it will give me a false sense of security. also, using the current used / current heap lets you see how the JVM is resizing the heap and indicates if there is a memory. Several tomcat developers use Jmeter monitor for that purpose and so do I. If you don't believe, I would suggest changing it and run 20-30 tests with varying request rates and thread count. I noticed you're attending Worcester Polytech. Are you doing this for a degree? peter lin --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
