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From: "Anthony J. Biacco" <abiacco@formatdynamics.com>
Subject: RE: what is the upper limit of maximum heap memory for Tomcat with
  32-bit JVM running on Red Hat Linux 4 (32-bit)
thread-topic: what is the upper limit of maximum heap memory for Tomcat with
  32-bit JVM running on Red Hat Linux 4 (32-bit)
Date: Thu, 23 Jul 2009 19:13:55 -0600
thread-index: AcoL7Zcvzwa/yeANTNqnjI7S/ot2cgAA3aEgAAK/rBY=
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To: "Tomcat Users List" <users@tomcat.apache.org>

I would do option 2 also if I were him. I doubt his cpus are 32-bit =
though. I'm betting any dual core out there is 64-bit, though I wouldn't =
bet the farm on it. We use the 64-bit jvm on dual-core xeons without any =
problem (rhel5).

-Tony


Sent from my Windows Mobile=AE phone.

-----Original Message-----
From: Li,Henry <henryli@mdanderson.org>
Sent: Thursday, July 23, 2009 6:08 PM
To: 'Tomcat Users List' <users@tomcat.apache.org>; =
'alan@compulsivecreative.com' <alan@compulsivecreative.com>
Subject: RE: what is the upper limit of maximum heap memory for Tomcat =
with  32-bit JVM running on Red Hat Linux 4 (32-bit)

Thank you Alan for your help.=20
I use top to get the 4G free memory: Mem:   8309064k total,  3426680k =
used,  4882384k free,   163308k buffers.
Your are right, my 4 processors mean 4 cores (2 dual-core processors)
I think I will take your workaround #2.

Regards,
Henry


-----Original Message-----
From: Alan Chaney [mailto:alan@compulsivecreative.com]=20
Sent: Thursday, July 23, 2009 6:30 PM
To: Tomcat Users List
Subject: Re: what is the upper limit of maximum heap memory for Tomcat =
with 32-bit JVM running on Red Hat Linux 4 (32-bit)

You are using a 32 bit operating system and a 32 bit processor. To make=20
more than 4GB of ram available you must ensure that you have PAE support =

enabled in your kernel (search Google for Physical Address Extension)=20
which may mean re-compiling for RHEL 4 (see Red Hat). Your processor may =

not support it but I'd suspect that when you say 4 processors you=20
probably mean 4 cores and I believe all 4 core Intel CPUs do support=20
PAE. Re-reading your email I see that you say that you have 4.5G of free =

memory - how did you determine this? 'top'?


Even so, I cannot find any clear statement on the web that the 32 bit=20
JRE will be able to address more than 4G even if you do have PAE=20
enabled. I suspect not. Actually, 'suspect' is way too mild a term ... I =

would be completely astounded if you could...

Possible workarounds are:

1. Try running 2 JVMs ( when you have PAE enabled) - of course this may=20
not work in your application (you'd have to have two Tomcat instances.)

2. Your other 'workaround' is to install a 64 bit OS and a 64 bit JVM.=20
Then you can have 7G+ for the JVM.

Regards

Alan Chaney


Li,Henry wrote:
> My Tomcat is running on 32-bit Red Hat 4 (2.6.9-78.0.1.ELsmp), host =
server has 8G physical memory and 4 processors.
>  java version "1.4.2"  gcj (GCC) 3.4.6 20060404 (Red Hat 3.4.6-10)
> I got java.lang.OutOfMemoryError
> Current configuration: -Xms1024M -Xmx2304M
> The host server has about 4.5G free memory. When I tried to increase =
-Xmx2304M to -Xmx3000M, I got this error:
> Error occurred during initialization of VM, Could not reserve enough =
space for object heap
> The maximum # I can reach is -Xmx2680M.
> QUESTION: Is there an upper limit for -Xmx? What is the work around? =
How can I use my free memory on the server to
> get rid of the OutOfMemoryError?
>=20
> Thanks,
> Henry
>=20
>=20
>=20
>=20
> !DSPAM:4a68ee3b41041381456296!
>=20

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