VisualVM | 易学教程

Best way to measure Memory Usage of a Java Program?

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问题 I'm currently using VisualVM , but the problem I'm having is that I can't save the graphs it generates. I need to report some data about its memory usage and running time, though running time is easy to get with System.nanoTime() . I've also tried the NetBeans profiler but it isn't what I want, since I'm not looking for specific parts that would be slowing it down or anything, so that would be overkill. The biggest problem with it is that it eats up too much processing time. Also doesn't let

Monitor .NET Threads

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问题 Is there any way to monitor/log thread interactions in the .NET runtime much like VisualVM does for Java? I don't have a specific need at the moment but I think it would be nice to see how all the threads in my application interact. 回答1: I am unfamiliar with VisualVM in Java....but.... If you are trying to accomplish this programmatically...check out the WMI Performance Counters. I am currently working with them myself! MSDN Link to WMI Performance Counters Remember If you are trying see the

错误java.lang.OutOfMemoryError：超出了GC开销限制

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 我执行JUnit测试时收到以下错误消息： java.lang.OutOfMemoryError: GC overhead limit exceeded 我知道什么是 OutOfMemoryError ，但是GC开销限制是什么意思？我该如何解决？ #1楼该消息表示由于某种原因，垃圾收集器占用了过多的时间（默认情况下为该进程所有CPU时间的98％），并且每次运行时恢复的内存很少（默认为堆的2％）。这实际上意味着您的程序停止任何进展，并且一直在忙于仅运行垃圾回收。为了防止您的应用程序浪费CPU时间而不做任何事情，JVM抛出此 Error 以便您有机会诊断问题。我见过这种情况的罕见情况是，某些代码在一个已经非常受内存限制的环境中创建了大量的临时对象和大量的弱引用对象。请查看本文以了解详细信息（特别是本部分）。 #2楼当在垃圾回收上花费太多时间而返回的次数太少时，GC就会抛出此异常。 GC上花费了98％的CPU时间，并且不到2％的堆被恢复。此功能旨在防止应用程序长时间运行，而由于堆太小而几乎没有进展，甚至没有进展。您可以使用命令行选项 -XX:-UseGCOverheadLimit 将其关闭 -XX:-UseGCOverheadLimit 更多信息在这里编辑：看起来有人可以比我更快地输入:)

How Java VisualVM shows threads that are not running/finished?

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问题 For testing I've created a thread which has just sleep in it. And I know that GC doesnt collect them for a while even if their usage is done but when you dont keep them as an object after they complete their task they should've be gone. So for testing purposes I used Java VisualVM but this is the first time I'm using it. And I see all these timer threads lying around with 0ms but I can still see them. Is this normal? And what does this mean? If I spam thousands of them, will it slow down my

What is RMI TCP Accept, Attach Listener, and Signal Dispatcher in Visual VM?

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问题 I'm profiling a program with Visual VM. My program runs for a while and finally pops up a few plots using XChart showing the results. After the charts are displayed, I noticed in Visual VM some active threads "RMI TCP Accept", "Attach Listener", and "Signal Dispatcher". What are these threads? I assume they are there in connection with Visual VM only. Am I correct?? 回答1: Loosely answered by this post https://stackoverflow.com/a/7698906/573057 As you assume; Attach, Signal and RMI TCP Accept

What is RMI TCP Accept, Attach Listener, and Signal Dispatcher in Visual VM?

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Why does JMX connection to Amazon EC2 fail?

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问题 I set up JMX on one of services running on Amazon EC2 instance but it doesn't work properly. I'm using VisualVM to connect and after short period of pending it fails with timeout. Looks like it fails because of missing response data or lags. I checked that JMX port is enabled in security group and also tried with different port with no JMX enabled and also with port not enabled in security group settings and both fails immediately, so it looks different. My EC2 instance and desktop both have

Prevent program from crashing when showing allocation stack traces

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问题 Question Why does VisualVM terminate my program when attempting to view object allocation stack trace, and how do I fix it? I'm cleaning up an application which has a few memory problems, the biggest being creating a bunch of short-lived int[] which causes GC to fire like crazy: When I right click int[] and choose Take Snapshot and Show Allocation Stack Traces , my application closes and a warning box pops up saying Failed to obtain results snapshot. The application terminated : The closest

How do I tell visualvm where to find my source code?

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问题 I'm running VisualVM to profile a simple Java application. When I double-click on a method in the profiling pane (hoping to get more details on it), then it says "No source found for class ....". I know where the source is. How do I tell VisualVM where to look? 回答1: I took a stack dump of the VisualVM process while it was displaying that error dialog, and it seems that the problem lies in the class org.netbeans.modules.profiler.api.GoToSource, in the method openSourceImpl . This method tries

Total method time in Java VisualVM

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问题 In Java VisualVM, is there any way to display total method time, rather than "self time"? (The latter is not particularly useful, since it doesn't tell you anything about how much time methods actually take to run.) If not, is there any standalone free Java profiler that does calculate total method time? 回答1: Looking at the trace data in a "snapshot" view allows you to see the total as well as the self time. Press the "snapshot" button that appears about the table of results. This will create