问题描述
我想在我的VPS上运行一个用java编写的非常简单的bot。
我想限制jvm内存让我们说10MB（我怀疑它还需要更多）。
I'd like to run a very simple bot written in java on my VPS.I want to limit jvm memory to let's say 10MB (I doubt it would need any more).
我用以下命令运行机器人：
I'm running the bot with the following command:
但是 top 表明为java保留的实际内存是 144m （或者我在这里解释错误吗？）。
But top shows that actual memory reserved for java is 144m (or am I interpreting things wrong here?).
任何想法在这里可能出错？
Any ideas what can be wrong here?
Java版1.6.0_20Java（TM）SE运行时环境（版本1.6.0_20-b02）Java HotSpot（TM）客户端VM（版本16.3-b01，混合模式）
Java version "1.6.0_20" Java(TM) SE Runtime Environment (build 1.6.0_20-b02) Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode)
BTW。我正在运行CentOS - 如果重要的话。
BTW. I'm running CentOS - if it matters.
编辑：
感谢您的回答。
Thank you for your answers.
我不能真正接受它们中的任何一个，因为事实证明问题在于我选择编写程序的语言，而不是JVM本身。
I can't really accept any of them, since it turns out the problem lies within the language i choose to write the program, not the JVM itself.
推荐答案
-Xmx 指定最大Java 堆分配（ -Xms 指定min 堆分配）。 Java进程有自己的开销（实际的JVM等），加上加载的类和perm gen空间（通过 -XX：MaxPermSize = 128m 设置）位于值得。
-Xmx specifies the max Java heap allocation (-Xms specifies the min heap allocation). The Java process has its own overhead (the actual JVM etc), plus the loaded classes and the perm gen space (set via -XX:MaxPermSize=128m) sits outside of that value too.
将您的堆分配视为Java的内部工作空间，而不是整个过程。
Think of your heap allocation as simply Java's "internal working space", not the process as a whole.
尝试实验，你会明白我的意思：
Try experimenting and you'll see what I mean:
java -Xms512m -Xmx1024m ...
此外，尝试使用 JConsole 或 JVisualVM （两者都附带Sun / Oracle JDK），您将能够看到实际堆使用情况的图形表示（以及用于约束大小的设置）。
Also, try using a tool such as JConsole or JVisualVM (both are shipped with the Sun / Oracle JDK) and you'll be able to see graphical representations of the actual heap usage (and the settings you used to constrain the size).
最后，正如@Peter Lawrey所说的那样，常驻内存是关键数字 - 在你的情况下，JVM只使用16 MiB RSS（根据'top'）。只要JVM的堆没有被推入交换（非RAM），共享/虚拟分配就不会引起任何问题。同样，正如我在一些评论中所述，还有其他JVM可用 - Java能够在低资源或嵌入式平台上运行。
Finally, as @Peter Lawrey very rightly states, the resident memory is the crucial figure here - in your case the JVM is only using 16 MiB RSS (according to 'top'). The shared / virtual allocation won't cause any issues as long as the JVM's heap isn't pushed into swap (non-RAM). Again, as I've stated in some of the comments, there are other JVM's available - "Java" is quite capable of running on low resource or embedded platforms.
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