1) an unintentional static reference to an object remains after the object is no longer needed Can help debug unintentional object relation (Java language equivalent of a memory leak - an object that is no longer needed but is kept alive due to references through some path from the rootset).Parses a heap dump in binary format (e.g.Useful for browsing the object topology in a heap snaphot (a.k.a.Using jcmd to create a heap dump jcmd GC.heap_dump filename= jhat Useful for send diagnostic command requests to the JVM.Using jmap to create a heap dump jmap –dump:file= jcmd Using jmap to JVM heap details jmap –heap If you want to monitor memory usage (instead of current usage), use jstat.Recommended to use the latest utility, jcmd (since JDK 8) instead of jmap utility, for enhanced diagnostics and reduced performance overhead.Specially helpful to inspect underlying configurations and algorithms.Useful for printing out current memory-related statistics (heap summary, histogram of java object heap, class loader statistics, information on objects awaiting finalization, dump java heap in hprof binary format) for a running VM or core file.Command line tool shipped with standard JDK (no installation/setup process).Jstat gc options (Image: ) - here you can see the importance of learning Java Memory Model and Garbage Collection jmap Use the Java Agent profiler method but with different instrumentation rules to allow them to run without affecting performance in productionsĮxamples: AppDynamics, Stackify Retrace, New Relic, Dynatrace Usage Stats on Profiling ToolsĪccording to an interesting survey done by RebelLabs, the following are the pioneering profiling tools used by the companies. Show a less amount of details (with aggregations and sampling) - but mostly the right information which are smartly selected to have high relevance to common performance concerns.Great for monitoring applications live in production environments.Agent Profilers - Use Java Instrumentation API to inject code into the application Have in-depth access to application since the code is being rewritten at the bytecode level - allowing for any code running in application (written by us or came from 3rd party libraries) to be instrumented More complicated to writeĮxamples: XRebel, Stackify Prefix APM Tools.Aspect Profilers - Use aspect-oriented programming (AOP) to inject code into the start and end of specified methods (the injected code can start a timer and then report the elapsed time when the method finishes) Simple to set up Need to prior knowledge/guessing on what to profile.There are 2 types of implementations for Transaction Profilers.
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