各种Sun JVM的默认最大堆大小是多少？

Question

有人会认为查找列出不同JVM版本的默认最大堆大小的表格很容易......但是快速搜索没有找到这样的东西。

那么，各个Sun JVM的默认最大堆大小是多少？

- Jared

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我真的在寻找有关不同JVM版本中默认最大大小的参考资料。 - Jared

Answer 1

我完全理解你的问题，因为JVM的默认设置因供应商和版本而异。我也对正确的矩阵感兴趣。但是我只有Oracle Java 7文档:

引用:

根据系统配置在运行时选择默认值。 对于服务器部署， -Xms 和 -Xmx 通常设置为相同的值。 有关更多信息，请参见HotSpot Ergonomics

深入文档中的内部隐藏文档它说：

The following changes take effect with J2SE 5.0. Garbage Collector of Server VM Changed to Parallel Garbage Collector

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). You can override this default by using the -XX:+UseSerialGC command-line option to the java command. Initial Heap Size and Maximum Heap Size Changed for Parallel Garbage Collector

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 as follows.

Initial heap size: Larger of 1/64th of the machine's physical memory on the machine or some reasonable minimum. Before J2SE 5.0, the default initial heap size was a reasonable minimum, which varies by platform. 

Maximum heap size: Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0, the default maximum heap size was 64MB. 

Note: The boundaries and fractions given for the heap size are correct for J2SE 5.0. They are likely to be different in subsequent releases as computers get more powerful.

- alfonx

Answer 2

Jared，根据Java 1.5文档，默认的最大大小为64MB。

看一下非标准选项-Xmsn和-Xmxn。

- nandokakimoto