设置heap size 的地方

freey

On AIX 5.2 or later
If the heap size is 3 GB or greater, LDR_CNTRL=MAXDATA=0@DSA is set.
If the heap size is between 2.3 GB and 3 GB, LDR_CNTR=MAXDATA=0XB0000000@DSA is set.
If the heap size is less than 2.3 GB, LDR_CNTR=MAXDATA=0XA0000000@DSA is set.
也就是说如果在系统里设置了LDR_CNTRL=MAXDATA=0@DSA 那么就可以用到3G以上内存了.


On AIX 5.1
Although the very large address-space model is also available on AIX 5.1, the implementation differs. Consequently, the 1.4.1 SDK does not support the use of the very large address-space model on AIX 5.1. The JVM still sets LDR_CNTRL=MAXDATA based on the maximum size of the heap, but does not use the very large address-space model.
If the heap size is greater than 1 GB, LDR_CNTRL=MAXDATA is set to an appropriate value. Note that this is an inverse relationship because as the heap size increases, fewer segments are reserved through the LD_CNTRL=MAXDATA value. For example, for a 1 GB heap LDR_CNTRL=MAXDATA is set to 0X60000000, while for a 1.5 GB heap, the LDR_CNTRL=MAXDATA value is 0X40000000.

If the heap size is smaller than 1 GB, LDR_CNTRL=MAXDATA is set to 0X80000000

如果要用到大的segment,就是把 LDR_CNTRL=MAXDATA 所指定的heap size 设置得小些.

dennis2

还是用 64 位的 jvm 省事一些，只要你的应用中没有编译成 32 位的 JNI。Sun 的 jvm 运行 64 位是加个 -d64 的参数，IBM 的就不知道了，你得去自己查 IBM jdk 的文档了。

感觉就像当初 16 位 Windows 到 32 位 Windows 的转换一样 ... painful experience