Note that packages configured as “not profiled” (as seen in the first picture of the section) are counted as “a method’s own code”. if the method calls another method, it will not include that time). Self time: How much time the profiler observed the listed method spent executing the method’s own code (e.g.The key is to know how to read the information: Update: On Heroku you can use the following command to take a heap dump and automatically download it: $ heroku java:jmap -app -dyno Thread panel and monitoring thread stateĬPU sampling shows you where time is being spent on the application. If you’re connecting to a Docker container or Heroku dyno, you’ll be asked where to save the file remotely, and you’ll need to manually transfer the heap dump file to your local machine and open it with “ File > Load…”. One caveat of this functionality is that it only works seamlessly when VisualVM is accessing an app running natively on your machine. Your Java code will be suspended until this process finishes. BE CAREFUL: Taking a heap dump means stopping all application threads while a possibly multi-gigabyte file is written. The “ Heap Dump” button requests that the JVM take a heap dump. The “ Perform GC” button triggers a full garbage collection. Classes: number of classes loaded on VM (includes automatically-generated classes).Metaspace: a separate memory arena where classes and other JVM metadata are kept. ![]() Heap: the main memory arena where objects and arrays are kept.a fully-loaded thread will be at 25% on a four-core machine CPU: usage as a percentage of total machine resources, e.g.The Monitor panel presents at-a-glance info on the overall state of the VM: This is actually not the same picture as the one in the introduction. ![]() Double-click it to get the magic to happen. A new “ localhost:9010” entry should appear on the applications list. Go to File > Add JMX Connection… Use localhost:9010 as a target. Step 3: Now you’re all set to connect using VisualVM. Step 2: Then, when running your docker container, expose port 9010 to your local machine: $ docker-compose run -p 9010:9010 Step 1: Go to your docker-compose environment and add the JAVA_TOOL_OPTIONS environment variable with the following configuration: JAVA_TOOL_OPTIONS= .port=9010 .local.only=false .authenticate=false .ssl=false =localhost .rmi.port=9010 You’ll need to enable the VM remote management extensions by defining an environment variable and expose the management port outside of docker. Connecting VisualVM to a running application Local application running natively If you don’t have the latest version (or any version at all), go to VisualVM’s website and make some magic happen. As of this writing, the latest version is 1.3.9, which I recommend you use. If you have the javac command, you should also have visualvm or jvisualvm. Further exploration: Other suggested awesome JVM tools. ![]() ![]()
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