Wired Development

JMH is a tool to measure Java code that is executed within  micro-second time scales. You may ask the question why do I care about the performance of code that by definition is executed in a very short period of time? It is important to only optimise code that will have a significant effect on the overall application. Sometimes a small portion of the your application's code is executed many times or your latency requirements of your application is in the micro-second time scale. Once your application is performing as required it can be difficult to maintain that performance whilst making code changes. An automated collection of micro-benchmarks running on key components of your application is an invaluable tool in maintaining the required performance. As a starting point a history of your JMH results needs to be stored in order to analyse trends in benchmark results. Influx JMH reporter is an open source tool we have written that parses the JMH JSON results file from a ben

At TransFICC for MiFID compliance (as explained in my previous blog) we need to obtain the time of an event within 100 microsecond accuracy with respect to UTC. To achieve this in Java we first need to be able to obtain the time from the OS with better than millisecond precision. We can then make use of Precision Time Protocol (PTP) to ensure the system clock is synchronised to UTC with sufficient accuracy. Take a look at the excellent posts from Luke Bigum on how to achieve this . As of Java version 8 it is not possible to directly obtain the time with higher than millisecond precision. Java 8 System.currentTimeMillis() will return the time since the Unix epoch in milliseconds. Higher precision time is possible on some underlying systems such as Linux. On Linux the code that the OpenJDK JVM executes is: The full source can be found  here . The code makes the function call gettimeofday(). This returns the time since the Linux epoch in micro seconds however it is rounded to th