You will no longer need to restart the application and hope that the problem goes away. Historical information captured about the JVM’s CPU usage and individual threads’ CPU usage can be used to determine what is the real cause of the Java application’s high CPU usage. You may want to change the garbage collection algorithm or increase the heap and non-heap memory available to the JVM to alleviate the problem. If none of the application threads is taking much CPU, the aggregate CPU usage of the application threads is low and yet the Java application is taking CPU, suspect garbage collection activity in the JVM. If the CPU usage is due to an unexpected workload increase, you should see the number of threads increase, and even if each thread consumes a small amount of CPU, the aggregate may be significant. In this example, look in the class, createLogic method and line number 223.įigure 2: Identifying the cause of high JVM CPU usage
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The exact class, method and line of code can be determined. This information gives operations staff, service desk support, and developers exactly what they need to identify the cause of high CPU usage. If the thread is assigned a name in the application, the thread name is shown on the left-hand side of Figure 2 and the detailed stack trace is on the right-hand side. In this example, there is one high CPU thread.įigure 1: Diagnosing high CPU threads in the JVMĭetailed diagnosis of this metric reveals the stack trace – i.e., which line of code is the thread that is taking CPU executing. The existence of any high or medium CPU thread is indicative of an application bottleneck, i.e., a piece of inefficient code that is executing frequently and taking up CPU. High and medium CPU threads are defined as threads that take up more than 50% CPU and 30-50% CPU respectively. By periodically collecting these statistics, monitoring tools can correlate thread level performance information with the CPU usage of the Java application and answer the question “Why is the Java application taking high CPU?”.įigure 1 below depicts the eG Enterprise screen that monitors threads in a JVM. Using JMX, Java monitoring tools can explore what threads are running in the JVM, the state of each thread, the CPU usage of each thread etc. Managing and monitoring applications can be designed and developed using the Java Dynamic Management Kit. Those resources are represented by objects called MBeans (for Managed Bean). According to Wikipedia, Java Management Extensions is a Java technology that supplies tools for managing and monitoring applications, system objects, devices and service-oriented networks. Modern JVMs (1.5 and higher) support Java Management Instrumentation (JMX) APIs. It is, therefore, essential to identify the cause of the CPU spike: is it due to poorly designed application code, insufficient memory allocation, or an unexpectedly high workload? JVM Monitoring Can Assist with Diagnosis of CPU Issues Restarting an application will not solve a CPU usage problem – it only mitigates the problem for a short while, until the problem reappears.
The server capacity may not be sized sufficiently to handle the rate of requests coming in and in such a situation, the Java application may be doing work, trying to keep up with the workload.
Java applications may take high CPU resources for many reasons:
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A key question then is: how to troubleshoot high CPU usage of a Java application? Why Do Java Applications Take High CPU? Often the solution to this problem is to restart the application and, lo and behold, the problem goes away – only to reappear a few days later. When this happens, application response becomes sluggish and users begin to complain about slow response. If you have deployed a Java application in production, you’ve probably encountered a situation where the application suddenly starts to take up a large amount of CPU.