如何通过环境变量设置Java的最小和最大堆大小？

How do I set Java's min and max heap size through environment variables?

如何通过环境变量设置Java的最小和最大堆大小？

I know that the heap sizes can be set when launching java, but I would like to have this adjusted through environment variables on my server.

我知道在启动java时可以设置堆大小，但我希望通过我的服务器上的环境变量进行调整。

6 个解决方案

#1

You can't do it using environment variables directly. You need to use the set of "non standard" options that are passed to the java command. Run: java -X for details. The options you're looking for are -Xmx and -Xms (this is "initial" heap size, so probably what you're looking for.)

您无法直接使用环境变量。您需要使用传递给java命令的“非标准”选项集。运行：java -X了解详细信息。你正在寻找的选项是-Xmx和-Xms（这是“初始”堆大小，所以你可能正在寻找它。）

Some products like Ant or Tomcat might come with a batch script that looks for the JAVA_OPTS environment variable, but it's not part of the Java runtime. If you are using one of those products, you may be able to set the variable like:

Ant或Tomcat等产品可能附带一个查找JAVA_OPTS环境变量的批处理脚本，但它不是Java运行时的一部分。如果您使用其中一种产品，则可以将变量设置为：

set JAVA_OPTS="-Xms128m -Xmx256m"  

You can also take this approach with your own command line like:

您也可以使用自己的命令行来实现此方法：

set JAVA_OPTS="-Xms128m -Xmx256m"  
java ${JAVA_OPTS} MyClass

#2

If you want any java process, not just ant or Tomcat, to pick up options like -Xmx use the environment variable _JAVA_OPTIONS.

如果你想要任何java进程，而不仅仅是ant或Tomcat，来获取像-Xmx这样的选项，请使用环境变量_JAVA_OPTIONS。

In bash: export _JAVA_OPTIONS="-Xmx1g"

在bash中：export _JAVA_OPTIONS =“ - Xmx1g”

#3

Actually, there is a way to set global defaults for Sun's JVM via environment variables.

实际上，有一种方法可以通过环境变量为Sun的JVM设置全局默认值。

See How to set a java system property so that it is effective whenever I start JVM without adding it to the command line arguments.

请参阅如何设置java系统属性，以便每当我启动JVM而不将其添加到命令行参数时它都有效。

#4

You can't do it using environment variables. It's done via "non standard" options. Run: java -X for details. The options you're looking for are -Xmx and -Xms (this is "initial" heap size, so probably what you're looking for.)

你不能使用环境变量。它是通过“非标准”选项完成的。运行：java -X了解详细信息。你正在寻找的选项是-Xmx和-Xms（这是“初始”堆大小，所以你可能正在寻找它。）

#5

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

我认为您唯一的选择是将java包装在一个脚本中，该脚本将环境变量替换为命令行

#6

A couple of notes:

几个笔记：

1. Apache ant doesn't know anything about JAVA_OPTS, while Tomcat's startup scripts do. For Apache ant, use ANT_OPTS to affect the environment for the JVM that runs /ant/, but not for the things that ant might launch.

   Apache ant对JAVA_OPTS一无所知，而Tomcat的启动脚本也是如此。对于Apache ant，使用ANT_OPTS来影响运行/ ant /的JVM的环境，但不会影响ant可能启动的内容。

2. The maximum heap size you can set depends entirely on the environment: for most 32-bit systems, the maximum amount of heap space you can request, regardless of available memory, is in the 2GiB range. The largest heap on a 64-bit system is "really big". Also, you are practically limited by physical memory as well, since the heap is managed by the JVM and you don't want a lot of swapping going on to the disk.

   您可以设置的最大堆大小完全取决于环境：对于大多数32位系统，无论可用内存如何，您可以请求的最大堆空间量都在2GiB范围内。 64位系统上最大的堆“非常大”。此外，您实际上也受到物理内存的限制，因为堆由JVM管理，并且您不希望大量交换进入磁盘。

3. For server environments, you typically want to set -Xms and -Xmx to the same value: this will fix the size of the heap at a certain size and the garbage collector has less work to do because the heap will never have to be re-sized.

   对于服务器环境，您通常希望将-Xms和-Xmx设置为相同的值：这将以一定大小修复堆的大小，并且垃圾收集器的工作量较少，因为堆永远不必重新生成大小。