Re: Windows 7 and all my Java stuff.
On Wed, 25 Nov 2009 09:19:16 -0500, Lew wrote:
Thomas Pornin wrote:
(**) With PAE, available since the Pentium Pro (that's more than twelve
years ago), a 32-bit x86 system may use up to 64 GB of RAM, but not
simultaneously: each single process may use only 4 GB.
I'm aware of no 32b JVM that can specify a heap over about 1.8 GB; most
are lower. 32b Windows only allows up to 2GB per process or 3GB with a
switch. The JVM and permanent generation use some of that, leaving less
for the heap.
$ java -version
java version "1.6.0_15"
Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
Java HotSpot(TM) Server VM (build 14.1-b02, mixed mode)
$ java -jar -Xmx3700m some.jar
....
$ java -jar -Xmx3800m some.jar
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.
So, the limit on this particular Java application is somewhere between
3.7GB and 3.8GB of heap.
I should point out that this is a 32bit JVM running on a 64bit system
with 32GB of RAM. Nonetheless, the limit on a 32bit application is still
4GB despite the 64bit OS. What it does mean, though, is that any
individual application has got a much greater chance of getting the max.
address space because the entire system isn't limited to 4GB.
The same may be true of a PAE system, I don't know and can't test it.
--
Nigel Wade