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From "Mark Benussi" <mark_benu...@hotmail.com>
Subject RE: [OT] How much RAM can java use
Date Thu, 06 Oct 2005 21:31:02 GMT
This was probably one of the best threads I have 'listened' to in ages. I am
researching setting up my own Tomcat hosting. This is going to be of use.

-----Original Message-----
From: Leon Rosenberg [mailto:rosenberg.leon@googlemail.com] 
Sent: 06 October 2005 20:48
To: Tomcat Users List
Subject: Re: [OT] How much RAM can java use

Chuck, Ryan,

thanx, you were extremely helpful!

regards
Leon

On 10/6/05, J. Ryan Earl <ryan@dynaconnections.com> wrote:
> Leon Rosenberg wrote:
>
> >Debian 3.1, kernel 2.6.x-smp (32 bit)
> >or
> >Debian 3.1, kernel 2.6.x-smp-emt64 (64 bit)
> >
> >Hardware: AMD Opteron and Xeon64 (both 64 bit)
> >
> >SUN jdk1.5 and/or jdk1.4.2
> >
> >4 GB total RAM for 32-bit linux, with 3/1 memory partitioning
> >16GB total RAM for 64-bit linux.
> >
> >
> I've tested 32/64 bit JVMs extensively and done considerable amount of
> JAVA_OPTS tuning for my company's application.  On a 32-bit machine you
> can't reliably go above a -Xms=1600m without getting OOM errors.  With a
> 3/1 split your virtual page table size for the entire JVM process must
> be below 3GB total virtual memory.  That's 3GB allocated, not commited.
> The JVM allocates a lot more memory besides the heap.
>
> With the 64-bit JVMs, the sky's the limit, however the 64-bit address
> also make your application take up more space relative to a 32-bit JVM.
> A 3.2GB 64-bit heap space isn't going to double the amount of identical
> objects you can create as compared to a 32-bit 1.6GB heap space because
> all pointer references will occupy twice the space.
>
> -ryan
>
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