Maximum Java heap size of a 32-bit JVM on a 64-bit OS

Question

The question is not about the maximum heap size on a 32-bit OS, given that 32-bit OSes have a maximum addressable memory size of 4GB, and that the JVM\'s max heap size depen

Answer 1

We recently had some experience with this. We have ported from Solaris (x86-64 Version 5.10) to Linux (RedHat x86-64) recently and have realized that we have less memory available for a 32 bit JVM process on Linux than Solaris.

For Solaris this almost comes around to 4GB (http://www.oracle.com/technetwork/java/hotspotfaq-138619.html#gc_heap_32bit).

We ran our app with -Xms2560m -Xmx2560m -XX:MaxPermSize=512m -XX:PermSize=512m with no issues on Solaris for past couple of years. Tried to move it to linux and we had issues with random out of memory errors on start up. We could only get it to consistently start up on -Xms2300 -Xmx2300. Then we were advised of this by support.

A 32 bit process on Linux has a maximum addressable address space of 3gb (3072mb) whereas on Solaris it is the full 4gb (4096mb).