Java内存之谜（我有泄漏）？ [英] Java memory mystery (do I have a leak)?

问题描述

我在linux服务器上运行一个独立的Java问题。我用-Xmx256m启动了jvm。我附加了一个JMX监视器，可以看到堆永远不会真正通过256Mb。但是，在我的linux系统上运行top命令时，我可以看到：

I have a standalone Java problem running in a linux server. I started the jvm with -Xmx256m. I attached a JMX monitor and can see that the heap never really passes 256Mb. However, on my linux system when I run the top command I can see that:

1）首先，此进程的RES内存使用量约为350Mb。为什么？我想这是因为堆外的内存？

1) First of all, the RES memory usage of this process is around 350Mb. Why? I suppose this is because of memory outside of the heap?

2）其次，这个过程的VIRT内存使用量不断增长和增长。它永远不会停止！它现在显示在2500Mb！我有泄漏吗？但堆不会增加，它只是循环！

2) Secondly, the VIRT memory usage of this process just keeps growing and growing. It never stops! It now shows at 2500Mb! So do I have a leak? But heap doesn't increase, it just cycles!

最终这会带来一个问题，因为系统的交换不断增长，最终导致系统死亡。

Ultimately this poses a problem because the swap of the system keeps growing and eventually the system dies.

任何想法是怎么回事？

我想问的一个重要问题，这可能是我的代码而不是JVM，kernal等的一些情况。例如，如果线程数量不断增长，那将符合我的观察结果的描述？您可以建议我注意哪些类似的东西？

推荐答案

一些潜在的问题：

• 直接分配的缓冲区和内存映射文件在Java堆外部分配，无法方便地处理。


• 为每个新线程保留一个堆栈区域。


• 永久生成（代码和实习字符串）超出了通常的堆栈。这可能是一个问题，类加载器泄漏（通常在重新加载webapps时）。


• C堆可能正在泄漏。

• Direct allocated buffers and memory mapped files are allocated outside of the Java heap, and can't conveniently be disposed.
• An area of stack is reserved for each new thread.
• Permanent generation (code and interned strings) is outside of the usual stack. It can be a problem is class loaders leak (usually when reloading webapps).
• It's possible that the C heap is leaking.

pmap -x 应该显示你的记忆是如何消失的。

pmap -x should show how your memory has disappeared.

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