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Profiling with JVisualVM

In the Java programming language, JVisualVM is a Java monitoring and profiling tool or feature that helps Java software developers control, manage, and analyze the runtime behavior of Java applications.

JVisualVM can help Java users identify.

• Computer CPU usage on your current system hardware.
• Memory usage in the current system.
• Garbage-collection data activity tasks in the programming system.
• System memory leak behavior.
• Thread task problems.
• Slow class methods.
• Stops or blocks in system application performance.

What is JVisualVM in Java?

JVisualVM provides a graphical interface for Java programmers to monitor running tasks and activities in the JVM system running the application.

A typical JVisualVM monitoring workflow is as follows.

Java User Applications

            ↓

JVM Platform

           ↓

JVisualVM Applications

          ↓

Monitor/Profile Tool

          ↓

Find Interruptions in System Tasks

          ↓

Optimize Important Java Source Code

Starting the JVisualVM Application in Java.

After starting the Java IDE application on their computer, Java users should open the JVisualVM application.

Java applications running locally on their computer system may be displayed in the Local section.

Java users should then select an application to preview detailed information about the JVM application task. The availability and packaging of JVisualVM applications in Java may vary with modern Java JDK distributions. Therefore, Java users may need to install it separately manually.

Monitoring CPU and Memory Consumption with JVisualVM Applications in Java.

Java programs running in a Java user’s JVisualVM application provide detailed information about application usage consumption and current system task activity monitoring. Such as:

• Computer CPU resource usage on current system hardware.
• Heap usage details.
• Used heap details.
• Maximum heap details.
• Threads task details.
• Classes program details.
• GC task details.

Example of JVisualVM applications monitoring CPU and memory.

Heap Usage

1100 MB ┤ ╭──╮

900 MB ┤ ╭──╯ ╰──╮

700 MB ┤ ╭──╯ ╰──

500 MB ┤─╯

└──────────────────

Time of Use

If heap usage continues to increase without returning to the bottom level after garbage collection, this could be a signal to Java users, making it worth investigating.

CPU Profiling Concepts in JVisualVM Applications.

A profiler can help Java users identify basic steps or methods that use excessive Java system CPU time or resources.

Example of CPU Profiling.

Java users can find this detailed information on CPU resources used on their system.

Method CPU Time Detail Information

—————————————

OrderService.processOrders() 51%

PriceCalculator.calculate() 19%

DatabaseService.query() 21%

Other 9%

This detailed information on CPU consumption resources used on their system helps Java users indicate where to test, rather than having to guess which code is currently performing slowly.

A simple CPU profiling workflow is as follows.

Start your application

               ↓

Open the JVisualVM application

              ↓

Select your IDE application

             ↓

Start CPU profiling

             ↓

Manage slow task operation

             ↓

Stop CPU profiling

             ↓

Analyze your custom methods

Memory profiling in JVisualVM applications.

Using your existing Java program source code in the IDE, JVisualVM applications can help Java developers understand how much system memory resources their actively running application is using.

Example of memory profiling.

List<Order> orders = new ArrayList<>();

for (int p = 0; p < 3_000_000; p++) {

orders.add(new Order(i));

}

If your program keeps a lot of objects unnecessarily referenced, the usage of system memory resources can increase significantly.

Java users can check these elements in their memory profiling.

• Heap memory usage information.
• Object instance element usage.
• Major memory-using classes in the program.
• System memory garbage collection information.
• Heap dump detail information.

Heap dump in JVisualVM applications.

A heap dump in a Java program is a screenshot of the program objects currently in the Java heap.

It can help Java developers test suspected memory leak information.

Heap dump example.

Heap dump info

├── order

├── user

├── hashmap

├── string

└── …

If a Java user discovers in a heap dump that millions of source code objects of a particular type suddenly remain in memory, they can test what is keeping them reachable.

A common heap dump test pattern is as follows.

Increasing system memory usage

                 ↓

Taking a heap dump

                 ↓

Analyzing program objects

                 ↓

Finding unexpectedly retained program objects

                 ↓

Checking references

                 ↓

Using application code properly

Thread task monitoring in JVisualVM applications.

JVisualVM applications also provide detailed information about the threads being used in the system in Java programs. Java users can view it in:

JVisualVM applications thread state.

————————————————

main RUNNABLE

http-worker-1 WAITING

http-worker-2 RUNNABLE

database-worker BLOCKED

This can help identify Java threads.

• Blocked system threads tasks.
• Waiting threads task queues.
• Too many thread creation methods.
• Potential deadlock condition.
• Thread contention element.

Garbage collection in a Java JVisualVM application.

In the Java programming language, the JVisualVM GC can display information about all task activities occurring in the system.

Example of garbage collection.

Java application

              ↓

Creates program objects

              ↓

Heap fill method

              ↓

Garbage collection information data

             ↓

Unused class program objects removed

If garbage collection occurs too frequently in a Java program, or takes too much CPU time, it may indicate excessive object allocation or incorrect JVM/application configuration.

Example of finding a performance problem in Java.

Understandably, this method may be slow for Java users.

public void processOrders(List<Order> orders) {

for (Order order : orders) {

calculatePrice(order);

sendNotification(order);

}

}

In this, you profile existing Java source code instead of immediately modifying or replacing it.

This is understandable to Java users.

processOrders() 100%

├── countRate() 23%

└── sendNotification() 77%

Profiling results in Java indicate that the sendNotification() function should be tested.

The key principle is.

Measure it first, then manually optimize it as needed.

Main Difference Between Java Jvisualvm Vs Ide Debugger

Conclusion of Profiling with JVisualVM.

JVisualVM, along with the Java IDE program, helps Java users understand or analyze in detail what the JVM is doing while running their Java program application. This is particularly useful for examining CPU bottlenecks, system memory usage, garbage collection data, and thread behavior, rather than simply running a step-by-step execution of Java source code.