Java application performance tuning should rely on tools and data rather than guesswork. 1. Use JVM's own tools such as jstat to analyze GC, jstack to troubleshoot thread problems, and jmap and MAT analyze memory leaks; 2. Visual tools such as JProfiler, YourKit, and VisualVM can intuitively view the time-consuming of calling links and methods; 3. APM tools such as SkyWalking, Pinpoint, and New Relic support full-link monitoring and distributed tracking; 4. Combining logs and Prometheus Grafana to achieve indicator monitoring and trend warning. Choosing tools rationally and understanding the results is key.

In fact, Java application performance tuning is often not based on guessing, but on tools and data. It is difficult to find the real bottleneck just by feeling, especially in online environments or complex business scenarios. To truly understand where the application is slow, where the card is tight, and where the resources are tight, we must rely on appropriate performance analysis tools and methods.

Below are some common Java performance analysis tools and tips suitable for daily troubleshooting and optimizing code.

1. Use the monitoring tools that come with JVM

JVM provides some basic but very practical command line tools, such as jstat, jstack, and jmap. They do not require additional installation and can be used.

• jstat : Check the GC situation, such as the frequency and time-consuming of Young GC and Full GC. If you find frequent Full GCs, it may have memory leaks or the parameter settings are unreasonable.
• jstack : Print thread stack information to troubleshoot deadlocks, thread blocking and other problems. You can basically locate the problem by finding the thread ID that occupies a high CPU and then viewing the specific stack through jstack.
• jmap MAT : generates a heap dump and analyzes memory usage with the Eclipse MAT tool. Suitable for troubleshooting memory leaks, large object occupation and other problems.

Although these tools look original, they are particularly useful when the server cannot install graphical tools.

2. Use visual performance analysis tools (such as JProfiler, YourKit, VisualVM)

If you need to see more intuitive information about calling links, CPU time-consuming distribution, memory allocation, etc., graphical tools will be more suitable.

• JProfiler is a good choice. It supports remote connections and can view thread status, memory allocation hotspots, method execution time, etc. in real time. In particular, its "Hot Spots" function can directly tell you which methods are the most time-consuming.
• YourKit has similar functions and a friendly interface, suitable for in-depth analysis.
• VisualVM is free. Although its functions are not as powerful as the previous two, it is enough for general problem troubleshooting.

This type of tool usually needs to add an agent parameter at startup, such as -agentpath:/path/to/jprofiler/bin/agent.so , and then connect through the client to start sampling.

3. Use APM tools for full-link monitoring (such as SkyWalking, Pinpoint, New Relic)

For microservice architectures, local debugging alone is no longer enough. You need to look at how the request flows from a holistic perspective, which service responds slowly, whether there is slow SQL, whether third-party calls are abnormal, etc.

• SkyWalking is a domestic open source APM tool with simple deployment and supports automatic point burial. It can track the entire call chain, and can also display JVM status, SQL execution details, etc.
• Pinpoint comes from South Korea and is also an old distributed tracking system with a clear UI interface and is suitable for medium and large projects.
• New Relic is a relatively popular business tool abroad, with comprehensive functions and rich charts, suitable for enterprise-level users.

APM tools generally implement non-invasive monitoring through Java Agent, and only need to add agent parameters to the startup script to take effect.

4. Use log metric monitoring in combination (such as Prometheus Grafana)

In addition to specialized performance analysis tools, log and metric monitoring are also an indispensable part.

• Logging on critical paths to record processing time and context information can help you quickly locate where the problem occurs.
• Combined with Prometheus to grab JVM indicators, such as heap memory usage, GC number, thread number, etc., and then display the trend chart through Grafana, you can discover potential risks in advance.
• If you use Spring Boot, you can directly enable Actuator Micrometer to easily access Prometheus.

This method is suitable for long-term monitoring and is convenient for alarm configuration.

In general, Java performance analysis is not a one-time transaction, but requires choosing the right combination of tools based on different scenarios. During the development stage, JProfiler or VisualVM can be used to quickly locate problems; after it is launched, it depends on APM and monitoring system to continuously observe the operating status. Although there are many tools, the key is to know when to use what and how to interpret the results.

Basically all of this is it, but it is not difficult to ignore details, but you still have to try it more.

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