xmx和MaxRAM JVM参数之间有什么区别? [英] What is the difference between xmx and MaxRAM JVM parameters?

问题描述

MaxRAM :

基于计算机上的内存量.用于堆的内存比例由命令行选项InitialRAMFraction和MaxRAMFraction控制 [...] MaxRAM的值取决于平台.

based on the amount of memory on the machine. The proportion of memory to use for the heap is controlled by the command-line options InitialRAMFraction and MaxRAMFraction [...] The value of MaxRAM is platform-dependent.

Xmx :

-Xmxn 指定内存分配池的最大大小(以字节为单位).此值必须是大于2 MB的1024的倍数.追加字母k或K表示千字节，或者追加m或M表示兆字节.默认值为64MB.在Solaris 7和Solaris 8 SPARC平台上，此值的上限大约为4000m，在Solaris 2.6和x86平台上，该值的上限为2000m(减去开销).

-Xmxn Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 64MB. The upper limit for this value will be approximately 4000m on Solaris 7 and Solaris 8 SPARC platforms and 2000m on Solaris 2.6 and x86 platforms, minus overhead amounts.

据我了解，两者均定义heap的大小.不?建议使用什么:Xmx或MaxRAM?如果我同时使用两个卵子?

As I understand both define heap size. No? What is recommended to use: Xmx or MaxRAM? If I use both which one ovverides another?

推荐答案

-Xmx指定堆的精确上限.这是设置堆大小的首选方法.

-Xmx specifies the precise upper limit for the heap. It is the preferred way to set the heap size.

-XX:MaxRAM不会直接定义堆大小.取而代之的是，此参数在根据人体工程学计算堆限制时会覆盖物理RAM的实际数量.

-XX:MaxRAM does not define the heap size directly. Instead this parameter overrides the actual amount of physical RAM when calculating the heap limits basing on ergonomics.

如果设置了-Xmx，则从不使用MaxRAM.否则，估计最大堆大小 ¹ 为

If -Xmx is set, MaxRAM is never used. Otherwise the maximum heap size is estimated¹ as

MaxHeapSize = MaxRAM * MaxRAMPercentage / 100% (default MaxRAMPercentage=25)

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¹ 实际的

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¹ The actual algorithm is a bit more complicated and depends on other parameters.

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