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I'm a Software Engineer working at WSO2. Please check my company profile at http://wso2.com/about/team/isuru-perera/

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Specifying a custom Event Settings file for Java Flight Recorder

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When you are using Java Flight Recorder (JFR), the JFR will use an event settings file to check which event types to record. By default in JFR, there are two settings, "default" and "profile". The default setting is recommended for Continuous Recordings as it has very low overhead (typically less than 1% overhead). The profile setting has more events and useful when profiling the application. As mentioned in my previous blog post regarding  Java Flight Recorder Continuous Recordings , we use following arguments to do a Continuous Recording. -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:FlightRecorderOptions=defaultrecording=true,disk=true,repository=./tmp,dumponexit=true,dumponexitpath=./ Note: According to the Oracle documentation on " java " command, we should be able to specify "settings" parameter to the -XX:FlightRecorderOptions. However, the settings parameter has no effect when used with the -XX:FlightRecorderOptions and
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Flame Graphs with Java Flight Recordings

Flame Graphs Brendon D. Gregg , who is a computer performance analyst , has created  Flame Graphs to visualize stack traces in an interactive way. You must watch his talk at USENIX/LISA13 , titled Blazing Performance with Flame Graphs , which explains Flame Graphs in detail. There can be different types of flame graphs and I'm focusing on  CPU Flame Graphs  with Java in this blog post. Please look at the Flame Graphs Description  to understand the Flame Graph visualization. CPU Flame Graphs and Java Stack Traces As  Brendon  mentioned in his talk, understanding why CPUs are busy is very important when analyzing performance.  CPU Flame Graphs  is a good way to identify hot methods from sampled stack traces. In order to generate CPU Flame Graphs for Java Stack Traces , we need a way to get sample stack traces. Brendon has given examples to use jstack  and Google's lightweight-java-profiler . Please refer to his perl program on generating  CPU Flame G
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Benchmarking Java Locks with Counters

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These days I am analyzing some Java Flight Recordings from taken from WSO2 API Manager performance tests and I found out that main processing threads were in "BLOCKED" state in some situations. The threads were mainly blocked due to "synchronized" methods in Java. Synchronizing the methods in a critical section of request processing causes bottlenecks and it has an impact on the throughput and overall latency. Then I was thinking whether we could avoid synchronizing the whole method. The main problem with synchronized is that only one thread can run that critical section. When it comes to consumer/producer scenarios, we may need to give read access to data in some threads and write access to a thread to edit data exclusively. Java provides ReadWriteLock for these kinds of scenarios. Java 8 provides another kind of lock named StampedLock . The StampedLock provides an alternative way to the standard  ReadWriteLock  and it also supports optimistic
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