Question on Java JVM size

[Trojan36]

Need a JVM with alot of memory. Tried with heap bumped to 3008, but is not large enough. But the JVM would not start when set to anything larger. Using Java 1.4.2.10 for PA-Risc 32-bit OS. Thx in advance.

[Dennis Handly]

>Using Java 1.4.2.10 for PA-RISC 32-bit OS.

Are you sure you have a 32 bit kernel?
What does "model" show?
If you have a 64 bit kernel, you could use 64 bit java, unless you use JNIs and they are only in 32 bit.

3 Gb is about the biggest heap you can get in 32 bit mode.

[Trojan36]

Hi Dennis,

On Itanium, is the default JVM 64 bit? Is there a 32-bit or does it simply not exist on Itanium? (HPUX 11.23 with Java 1.5)

thx in advance

[Dennis Handly]

>is the default JVM 64 bit? Is there a 32-bit or does it simply not exist on Integrity?

The default is 32 bit.

[Trojan36]

Dennis,

I see that there is a â d64 option.
If I need a lot of memory, I can go with that.

If I do not need that much memory (Say 2 â 2.5 gig) should I stay with 32-bit?

Thx

[Jov]

Hi,

If you can run the 64bit version of JVM and your application is compatible, then its recommended as when running 32bit, there is an extra emulation layer which the OS has to perform.



Jov

[Trojan36]

What do you mean by emulation? Can you explain that a bit more? Thx

[Dennis Handly]

>If I do not need that much memory (Say 2 or 2.5 gig) should I stay with 32-bit?

I would suggest if you need <= 1 Gb, you should use 32 bit, otherwise 64 bit.

>Jov: as when running 32bit, there is an extra emulation layer which the OS has to perform.

As Trojan36 asked, what do you mean here?
For PA, there isn't anything extra. For IPF there may be a trivial amount of address conversion on system calls.

[Jov]

Hi,

Disregard my comment emulation comment as I mis-read the OS version (read it as IPF).

Anyway, extracted from the following URL
http://docs.hp.com/en/SDKRTE142RN/sdk_rnotes_1.4.2.10.html#hotspot

# Large heap sizes
Heaps up to 3.5GB are supported on HP-UX 11.23 (11i v2) (no patches required), and up to 3GB on HP-UX 11.11 PA (11i v1) with the installation of patches. Refer to the sections on expanding memory in the HP-UX Programmer's Guide for Java 2 at: Expanding Memory

# 64-bit mode
Supported by using the option -d64. For further information, refer to the HP-UX Programmer's Guide for Java 2 at HotSpot Technology Tools and Commands#-d64


HTH

Jov