非服务器类计算机上Xmx，Xms，MaxPermSize的默认值 [英] Default values for Xmx, Xms, MaxPermSize on non-server-class machines

问题描述

非服务器类计算机上的Java 6中以下选项的默认值是什么?

• -Xmx
• -XX:MaxPermSize

Oracle的文档指出: :

Oracle's documentation states that:

在运行服务器VM的服务器级计算机上，垃圾收集器(GC)已从以前的串行收集器(-XX:+ UseSerialGC)更改为并行收集器(-XX:+ UseParallelGC).

On server-class machines running the server VM, the garbage collector (GC) has changed from the previous serial collector (-XX:+UseSerialGC) to a parallel collector (-XX:+UseParallelGC).

和

在运行带有并行垃圾收集器(-XX:+ UseParallelGC)的VM(客户端或服务器)的服务器级计算机上，初始堆大小和最大堆大小已更改

On server-class machines running either VM (client or server) with the parallel garbage collector (-XX:+UseParallelGC) the initial heap size and maximum heap size have changed

该页面未描述非服务器类计算机的默认值，仅描述了初始值，例如，初始堆大小为合理的最小值".查看手册页" java命令针对-Xms有以下内容:

The page doesn't describe the defaults for non-server-class machines, only that, for example, the initial heap size is "a reasonable minimum". Looking at the 'man page' for the java command there is the following against -Xms:

在运行时根据系统配置选择默认值

The default value is chosen at runtime based on system configuration

推荐答案

Windows 7/32位上JDK 1.6.0_29的默认值:

Default values for JDK 1.6.0_29 on Windows 7/32-bit:

-Xmx256m
-XX:MaxPermSize=64m

这些选项的值也可以通过以下命令打印:

Also value of these option can be printed by following command:

java -XX:+UnlockExperimentalVMOptions -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version 2>&1

然后查找MaxHeapSize和MaxPermSize键并查看默认值.

Then look for MaxHeapSize and MaxPermSize keys and see default values.

uintx InitialHeapSize                          := 199947456       {product}
uintx MaxHeapSize                              := 268435456       {product}           
uintx MaxPermSize                               = 67108864        {pd product}        

此处是终极Hotspot VM选项备忘单，其中包含JDK的最后5个版本的默认设置和说明(7、8、9、10和11).

Here is the Ultimate HotSpot VM Options Cheat Sheet with defaults and descriptions for last 5 versions of JDK (7, 8, 9, 10 & 11).

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