A Java Thread Dump is often used for analyzing scalability issues, hangs or deadlocks. It contains the stack trace for every thread and the locks/monitors a thread holds or waits for. Sometimes it may be useful to create a visual illustration of the dependencies between the blocked threads to be used for a document or a presentation. I would like to introduce a little perl script I wrote for this purpose.Continue reading "Visualize wait-for graph for Java threads"
A lot of times I see people looking at the load average for a health check of a machine. This may give a hint if the machine is busy but it doesn't help to locate the cause. I will show in this article that two totally different workloads will result in exactly the same load average profile. This effectively make the load average alone a useless measurement in root cause analysis.Continue reading "Tuning by Load Average - Not!"
In August 2011 Dave Abercrombie wrote an article about the Universal Scalability Law (USL) in an Oracle OLTP database. He used Mathematica for his calculations and wanted to provide a solution based on R later. Currently I am keen to learn more about the Universal Scalability Law and therefore I decided to transform his calculations into R code myself.Continue reading "Universal Scalability Law in Oracle"