Re: Windows 7 and all my Java stuff.
On Wed, 25 Nov 2009 16:27:18 +0000, DuncanIdaho wrote:
Nigel Wade wrote:
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.
snip
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.
OK well I've ordered my new laptop with Windows 7
By the way http://java.sun.com/javase/downloads/widget/jdk6.jsp offers
JDK 6 Update 17 for Windows and Windows x64 where the archive for the 64
bit version is smaller than that for the 32 bit version by around 8MB,
interesting huh,
Well, the Linux 64bit version is about 1MB larger. It doesn't really tell
you anything about the unpacked size, or the size of running JVM.
also, apparently the 64 bit release can be used in 32
bit mode...
Maybe, maybe not:
$ /usr/java/jdk1.6.0_17/bin/java -version
java version "1.6.0_17"
Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)
$ /usr/java/jdk1.6.0_17/bin/java -version -d32
Running a 32-bit JVM is not supported on this platform.
I don't know whether it works on Windows.
Anyway, it will be interesting to see just how big the heap can be with
a 64bit JVM running on a 64bit system. Roll on delivery day.
Whatever the limit of your VM is, presumably. Probably RAM+swap, or the
administrator/OS defined per-process VM limit. You can request max. heap
size much more than the available VM, but it's not actually physically
allocated until required, for example:
$ /usr/java/jdk1.6.0_17/bin/java -Xmx128000m -jar some.jar
works on a system with only 32GB RAM.
If, however, I restrict the per-process VM to 20GB using:
$ ulimit -v 20000000
I get:
$ /usr/java/jdk1.6.0_17/bin/java -Xmx20000m -jar dist/MP3FileCopier.jar .
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.
but I can request 19GB.
As I said elsethread, taking up a few MB of extra space for 64bit
addresses is not something to be overly concerned about.
--
Nigel Wade