Translator's note: the desire to translate the note appeared in the early June morning after reading it in a half-asleep state in a subway car. Target Audience: People taking their first steps in the world of Java and by the nature of their basic technical background or desire are very eager to get under the hood of Java and learn all the "electrodynamic" processes. I am sure that for those who read this will be the starting point of a journey into the world of JVM and GC tuning. Favorable wind! The original article is here As a developer, you spend countless hours cleaning out bugs from a Java application and getting performance where you need it. During testing, you notice that the application gradually slows down, and in the end it completely crashes or simply shows poor performance. Ultimately admit that memory leaks occur. Garbage collector Java does its best to deal with these leaks. But there are only a lot of things to do when faced with situations like these. You need ways to identify memory leak calls, identify the causes, and understand the role of the Java garbage collector in the overall performance of an application.
Main Symptoms of Java Memory Leaks
There are several symptoms that indicate that an application has memory leak problems. A slight drop in performance, rather than an abrupt application crash, only indicates a memory leak. The problem can happen every time you work, or only when the application starts working with a large amount of data, or, conversely, you start scaling the application. The application will probably show an out-of-memory error once the leak has consumed all available memory resources. By restarting the application and hoping for the best, you will encounter repeated crashes until the leak is fixed. In general, memory leaks happen when object references accumulate instead of freeing memory. They take up all available memory and make it impossible for an application to access the resources it needs.
Configuration errors that look like memory leaks
Before you look into the situations that cause Java memory problems and analyze it, you need to make sure that the research is not related to a completely different task. Some out-of-memory errors are due to various errors, such as configuration errors. The application may be running out of heap space or conflicting with other applications on the system. If you start talking about out-of-memory issues but can't figure out what's causing the leak, look at your application differently. You will find that you need to make changes to the finalization stream or increase the amount of permanent generation space, which is the JVM memory area for storing the description of Java classes and some additional data.
Benefits of Memory Monitoring Tools
Memory monitoring tools give greater visibility into the use of available resources by a Java application. By using this software, you are taking a step towards narrowing down the root of memory leaks and other performance incidents. The tools come in several categories and you may need to use a lot of applications to figure out how to start properly naming the problem and what went wrong, even if you're dealing with memory leaks. Heap dump (heap dump) files provide the necessary information for the analysis of Java memory. In this case, you need to use two tools, one to generate a dump file and another to analyze it in detail. Such a decision gives detailed information about what is happening with the application. Once the tool indicates the places of possible problems and works to narrow the area, to locate the exact location of the incident. And this period of time is the time of the longest and most moody part of trial and error. The memory analyzer indicates several problems in the code, but you are not absolutely sure what problems your application has encountered. If you are still experiencing the same error, start over and work on another possible error. Make one change at a time and try to duplicate the error. You will need to let the application run for a while to duplicate the error conditions. If a memory leak occurs during the first test, don't forget to test the application under load. The application may work fine with a small amount of data, but may re-throw the old errors when working with a large amount of data. If the same error still occurs, you need to start over and analyze another possible cause. Memory monitoring tools prove useful once the application is fully operational. You can remotely monitor JVM performance and proactively detect failures before a developer dives into the problem and collects historical performance data to help them improve their programming techniques in the future and see how Java performs under heavy load. Many solutions include alert modes "danger" or other similar modes, and the developer can immediately know what is going wrong. Every developer doesn't want a critical application in production to crash and cause them to lose tens or hundreds of thousands of dollars during application downtime, therefore, memory monitoring tools reduce developer response time. Memory monitoring applications allow you to start the diagnostic process instantly, instead of asking you to go to the customer, where no one will tell you exactly what error happened or what error code the application generated. If you find yourself frequently diving into memory and performance issues in your Java application, take a hard look at the testing process. Identify each weak area in the development process and change testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and further ensure that the entire application has a lasting impact. instead of asking you to go to the customer, where no one will tell you exactly what error happened or what error code the application generated. If you find yourself frequently diving into memory and performance issues in your Java application, take a hard look at the testing process. Identify each weak area in the development process and change testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and further ensure that the entire application has a lasting impact. instead of asking you to go to the customer, where no one will tell you exactly what error happened or what error code the application generated. If you find yourself frequently diving into memory and performance issues in your Java application, take a hard look at the testing process. Identify each weak area in the development process and change testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and further ensure that the entire application has a lasting impact. Identify each weak area in the development process and change testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and further ensure that the entire application has a lasting impact. Identify each weak area in the development process and change testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and further ensure that the entire application has a lasting impact.
Role of Garbage Collector on Java Memory and Memory Leaks
The Garbage Collector in Java plays a key role in application performance and memory usage. It looks for unused (dead) objects and deletes them. These objects no longer take up memory, so your application continues to keep resources available. Sometimes an application doesn't give the GC enough time or resources to remove dead objects and they pile up. You might run into a situation where you're actively accessing objects that you think are dead. The garbage collector can't do anything about it, because its automated memory management mechanism bypasses active objects. Normally, the garbage collector runs offline, but you need to tune its behavior to deal with severe memory problems. However, the GC itself can lead to performance problems.
GC areas
The garbage collector divides objects into different regions to optimize collection. Young Generation features objects that die off quickly. The garbage collector often works in this area, from the moment it should be cleaning up. Objects remaining alive after reaching a certain period pass into the Old Generation. Objects stay in the Old Generation area for a long time, and they are not removed by the collector as often. However, when the collector is running on a scope, the application goes through a larger operation where the collector looks through live objects to clean up the garbage. As a result, the application objects are in the permanent generation target area. Typically, these objects include the required JVM metadata. The application does not generate much garbage in the Permanent Generation, but needs a collector to remove classes when the classes are no longer needed.
Relationship between Garbage Collector and response time
The garbage collector, regardless of the execution priority of application threads, stops them without waiting for completion. This phenomenon is called the "Stop the World" event. The Young Generation region of the garbage collector has little effect on performance, but problems are noticeable if the GC performs heavy cleanup. You end up in a situation where the Young Generation minor garbage collection is constantly running or the Old Generation goes into an uncontrolled state. In such a situation, one needs to balance the frequency of the Young Generation with the performance that requires increasing the size of this collector area. The Permanent Generation and Old Generation regions of the garbage collector significantly affect application performance and memory usage. This major garbage cleanup operation goes through the heap, to push out dead objects. The process takes longer than a minor build and the performance impact may be longer. When the scrubbing intensity is high and the size of the Old Generation area is large, the performance of the whole application is bogged down due to "Stop the world" events. Garbage collection optimization requires monitoring how often a program is run, the impact on overall performance, and ways to tweak application settings to reduce the frequency of monitoring. You may need to identify the same object placed more than once, without the application needing to fence off the placement, or you need to find compression points holding back the entire system. Getting the balance right requires paying close attention to everything from CPU load to your garbage collector cycles, especially if Young and Old Generation are imbalanced. Memory leak addressing and garbage collection optimizations help improve the performance of a Java application. You are literally juggling a lot of moving parts. But with the right troubleshooting approach and analysis tools designed to give rigorous visibility, you will reach the light at the end of the tunnel. Otherwise, you are tormented with the resulting performance problems. Careful memory allocation and monitoring is critical in a Java application. You need to take full control of the interaction between garbage collection, object disposal, and performance in order to optimize your application and avoid out-of-memory bugs. Monitoring tools allow you to stay on top, to detect potential problems and highlight memory usage trends so that you take a proactive approach to troubleshooting. Memory leaks often show inefficiency in troubleshooting in the usual way, especially if you encounter incorrect configuration parameter values, but addressing memory issues can help you quickly avoid incidents that get in your way. The excellence of Java memory tuning and GC makes your development process much easier.
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