http://blog.csdn.net/youthon/...

這篇文章說Linux上，系統(tǒng)進(jìn)程內(nèi)存最大限制，32位和64位理論上最大都可達(dá)到4G

而另外的文章說，這個(gè)最大限制可以測試，用類似于下面命令：

 java -Xmx503446m -version
 

如果不報(bào)錯(cuò)，說明能分配500G左右
我試了一下，

$ java -Xmx603446m -version 
Java HotSpot(TM) 64-Bit Server VM warning: INFO:         
os::commit_memory(0x00007e6915650000, 19773718528, 0) failed; 
error='Cannot allocate memory' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment 
to continue.
# Native memory allocation (mmap) failed to map 19773718528 
bytes for committing reserved memory.
$ java -Xmx503446m -version 
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

可見500G左右沒問題，600G就不行了

但是這個(gè)遠(yuǎn)超4G了啊，如何理解？