如何在Windows中进行堆转储，停机时间最短？ [英] How to take a heap dump in windows with minimum downtime?

问题描述

我想知道为什么Elasticsearch节点上的JVM堆使用率一直在80％以上。为了做到这一点，我通过运行

  jmap.exe -heap：format = b 5348 
  

（5348是进程ID）。然后我可以使用VisualVM分析转储。

问题是，在执行转储时，$ code> jmap 暂停JVM，所以节点基本上离线了大约5分钟。

本文提出了一种更快速的方法，它依赖于在Linux上使用 gdb 的coredump。我已经尝试过WinDbg，它创建了一个核心转储，但是我无法在VisualVM中使用它。

Windows有类似的方法吗？

解决方案

在使用coredump后，您可以使用 WinDbg ，您需要通过运行

  jmap -heap：format来提取堆转储= bC：\Program Files\Java\ ... \bin\java.execore.mdmp 
  

这可以离线完成;不需要与运行的Java进程交互。然后，您将可以在VisualVM中打开生成的 heap.bin 。

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或者，您可以使用类别直方图。它的产生速度比完全堆转储速度快。

  jmap -histo< PID> 
  

它显示了实例占用堆中最多空间的类的列表。这个信息通常足以让你知道内存丢失的位置。

I want to figure out why JVM heap usage on Elasticsearch node is staying consistently above 80%. In order to do this, I take a heap dump by running

jmap.exe -heap:format=b 5348

(5348 is the Process ID). Then I can analyze the dump with VisualVM.

The problem is that jmap pauses the JVM while taking the dump, so the node is basically offline for around 5 minutes.

This article suggests a faster approach that relies on taking coredump with gdb on Linux. I already tried WinDbg, which created a core dump, but I couldn't use it in VisualVM.

Is there a similar approach for Windows? How one can take heap dumps in seconds, not minutes?

解决方案

After you've taken the coredump by WinDbg, you need to extract the heap dump from it by running

jmap -heap:format=b "C:\Program Files\Java\...\bin\java.exe" core.mdmp

This could be done offline; no interaction with running Java process needed. Then you will be able to open the generated heap.bin in VisualVM.

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Alternatively you may take the class histogram. It is produced a way faster than full heap dump.

jmap -histo <PID>

It shows you the list of classes whose instances occupy the most space in the heap. This information is often enough to get the idea of where's the memory lost.

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