来自Java的内存主机和内存参数xms和xmx之间的关系 [英] Relation between memory host and memory arguments xms and xmx from Java

问题描述

我有以下主机的内存详细信息：

I have the following host with the memory details:

$free -m
             total       used       free     shared    buffers     cached
Mem:          7872       7579        292         17        483       3983
-/+ buffers/cache:       3112       4759 
Swap:         2047         14       2033

我有一个使用params -Xms200m -Xmx200m 运行的java应用程序，有人可以解释一下为什么VCZ是3800076和RSS是来自 ps -aux 命令的241304（更多Java参数）

I have a java app running with the params -Xms200m -Xmx200m, could someone please explain me why the VCZ is 3800076 and the RSS is 241304 (which is more of the Java params)

：

66345     6773  0.2  2.9 3800076 241304 ?      Sl   Apr1  12:06 /apps/myapps/myapp1/java/bin/java -Xms200m -Xmx200m

推荐答案

Java进程使用的内存（如操作系统所见）不仅限于Java堆。还有更多的内存区域应该计算在内：

Memory used by Java process (as seen by the OS) is not only limited to Java Heap. There are a lot more memory areas that should be also counted:

• 元空间（类元数据所在的位置）;


• 代码缓存（JIT编译方法的存储和所有生成的代码）;


• 直接ByteBuffers;


• 内存映射文件，包括由JVM映射的文件，例如类路径上的所有JAR文件;


• 线程堆栈;


• JVM代码本身以及Java Runtime加载的所有动态库;


• 其他内部JVM结构。

• Metaspace (where class metadata resides);
• Code Cache (storage for JIT-compiled methods and all the generated code);
• Direct ByteBuffers;
• Memory-mapped files, including files mapped by JVM, e.g. all JAR files on the classpath;
• Thread stacks;
• JVM code itself and all the dynamic libraries loaded by Java Runtime;
• Other internal JVM structures.

使用 NativeMemoryTracking JDK功能，用于获取JVM使用的内存区域的详细分类：

Use NativeMemoryTracking JDK feature to get the detailed breakdown of memory areas used by JVM:

java -XX:NativeMemoryTracking=detail -XX:+UnlockDiagnosticVMOptions -XX:+PrintNMTStatistics

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