Tomcat服务器的JVM可用内存未返回操作系统 [英] Tomcat server's JVM free memory not returned to OS

问题描述

我的tomcat服务器表现很奇怪，它从系统分配了6GB的内存，但是超过4GB的标记为空闲".

My tomcat server is behaving strange, it has allocated 6GB of memory from system, but more than 4GB is marked as "free".

这是tomcat服务器状态的屏幕:

This is a screen from tomcat server status:

我了解JVM中的可用内存"的含义，但是我不明白为什么它不返回，因此在这种情况下至少要有3GB的内存返回系统.

I understand what "Free memory" in JVM means, but I do not understand why it is not returning lets say in this situation at least 3GB back to system.

Env:

• Java 8
• Tomcat 8
• Debian 8.3
• 计算机上的总内存:64 GB

推荐答案

由于尚未覆盖任何JVM选项，因此Tomcat使用默认的垃圾收集器，即JDK 8中的ParallelGC.

Since you haven't overridden any JVM options, Tomcat uses the default garbage collector which is ParallelGC in JDK 8.

ParallelGC不会取消提交堆内存.尝试-XX:+UseG1GC选项. G1垃圾收集器 能够将内存释放回操作系统.

ParallelGC does not uncommit heap memory. Try -XX:+UseG1GC option. G1 garbage collector is capable of releasing memory back to the OS.

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