Comments on: 32-bit or 64-bit JVM? How about a Hybrid?

By: Ismael Juma

Ismael Juma — Thu, 14 Jul 2011 17:33:59 +0000

Sorry Usman, the information you provided is not enough to help you. I suggest you ask on stackoverflow or a site like it.

By: Ismael Juma

Ismael Juma — Thu, 14 Jul 2011 17:32:58 +0000

Hi Jumar. Yes, it is enabled automatically when relevant if you’re using update 23 or later.

By: Jumar

Jumar — Thu, 14 Jul 2011 17:26:17 +0000

To clarify your last comment:
“This feature is enabled by default since JDK 6 Update 23″.
This means that as of jdk6u23, the option -XX:+UseCompressedOops is enabled automatically when relevent? Or just that this option is supported if specified as command line?

By: Stefan’s Kugel » Blog Archive » [Java] Faster with -XX:+UseCompressedOops or upgrade to jdk1.6.0_23

Sat, 18 Jun 2011 16:56:22 +0000

[...] the old 4GB limit, through some optimizations. There are plenty of good post with the details, e.g. http://blog.juma.me.uk/2008/10/14/32-bit-or-64-bit-jvm-how-about-a-hybrid/. Java 1.6.0_22 is the last version which has this option disabled by default. Since 1.6.0_23 it is [...]

By: Usman Aleem

Usman Aleem — Mon, 06 Jun 2011 19:27:16 +0000

Here is my problem i am working on a project which uses javaws(32 bit jre) and my application build on some wrappers C++. when i try to run it with 1024M it is working fine on 64bit machine windows7 but when i try to run it with 1536M. outof memory and very strange behavious observed like one program working fine and some time it even gives me null pointer exception on calling simple JFileChooser dialog etc. and then that application will never works unless restart my application or just hangs.

By: Ismael Juma

Ismael Juma — Fri, 25 Feb 2011 10:50:38 +0000

The feature I am talking about in the post and in the quoted sentence is -XX:+UseCompressedOops (not -XX:+ConcMarkSweepGC).

By: phoenix

phoenix — Thu, 24 Feb 2011 02:59:10 +0000

“This feature is enabled by default since JDK 6 Update 23″.
Is this mean that we don’t need add -X:+UseConcMarkSweepGC after JDK 6 Update 23? And how can we check if the JDK enabled this default? Thanks!

By: Ismael Juma

Ismael Juma — Thu, 20 Jan 2011 15:28:07 +0000

That is strange, what JVM version are you using?

Ismael

By: Ismael Juma

Ismael Juma — Thu, 20 Jan 2011 15:27:21 +0000

If it’s a pure Java application, you don’t need to recompile it. Note that you also have to check whether your container is pure Java (in which case changing the JVM is enough) or requires some configuration to run in 64-bit mode.

Best,
Ismael

By: Guliaiete

Guliaiete — Thu, 20 Jan 2011 15:20:36 +0000

Hi Guys
I have a pure java + Apple Web Object 5.5 web application, right now application is on 32bit processor with 32bit JVM having 16gb ram but still client get “java.lang.OutOfMemoryError: Java heap space” so we are planning to move it on 64bit jvm and 64 bit processor and 32 gb ram. Here my question is will i need to recompile my application before it live on production server or there is no need of recompilation? ..one more thing i want to mention it’s a pure java application no native code. Thanks in advance waiting for your response.

By: worldapp

worldapp — Wed, 03 Nov 2010 15:01:21 +0000

I tried each mode: both 64 bit (usual and compressed) and 32 bit
with our application.
-Xmx12500m -server -XX:+UseCompressedOops
In compressed mode it takes 10 times more to start. Export to SPSS takes also 20 times worse, but memory consumption is much better and faster in compressed mode (up to 40%). As for me, it could be helpfull for test applications and platphorms, if it did not take so much time to compute

By: Ismael Juma

Ismael Juma — Thu, 11 Feb 2010 20:51:21 +0000

No problem and good luck. :)

By: fpc

fpc — Thu, 11 Feb 2010 20:45:52 +0000

Thanks very much Ismael. I’ll give that a shot. :)

By: Ismael Juma

Ismael Juma — Thu, 11 Feb 2010 20:44:19 +0000

Hi fpc,

You need Java 6 Update 14 or newer (I recommend Java 6 Update 18 if you want to use this feature as it contains an improved version of it).

Best,
Ismael

By: fpc

fpc — Thu, 11 Feb 2010 20:41:43 +0000

Hi,

I tried adding “-XX:+UseCompressedOops” to our java options for running tomcat and I’m getting this error:
Unrecognized VM option ‘+UseCompressedOops’
Could not create the Java virtual machine.

We’re using java 1.6.0_12 and it is a 64 bit server (and 64 bit jvm). What might be causing this?
java -version
————-
java version “1.6.0_12″
Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
Java HotSpot(TM) 64-Bit Server VM (build 11.2-b01, mixed mode)
————-

Thanks in advance,
fpc

By: Kari’s World » Blog Archive » Oops, I did it again….

Kari’s World » Blog Archive » Oops, I did it again…. — Wed, 27 Jan 2010 18:27:33 +0000

[...] 32-bit or 64-bit JVM? How about a Hybrid? Load unsigned and better Compressed [...]

By: Knowtu » links for 2009-10-27

Knowtu » links for 2009-10-27 — Wed, 28 Oct 2009 01:05:50 +0000

[...] 32-bit or 64-bit JVM? How about a Hybrid? « Ismael Juma (tags: java performance 64) [...]

By: New JVM options and Scala iteration performance « Ismael Juma

New JVM options and Scala iteration performance « Ismael Juma — Mon, 26 Oct 2009 14:00:53 +0000

[...] on Q4, 2009 and it includes HotSpot 16. Even though JDK 6 Update 14 (HotSpot 14) introduced compressed references and scalar replacement, HotSpot 16 includes improved compressed references and many crucial fixes [...]

By: Sunil

Sunil — Thu, 30 Jul 2009 17:59:22 +0000

Juma,
We are using solaris10 32 bit JVM on our production servers with Sun one app server. As we are constatnly getting out of memory – heap error, I am planning to increase the heap size to 4G for JVM options. Current heap size is 2G and we have 8G memory available.

By: Ismael Juma

Ismael Juma — Wed, 08 Apr 2009 18:59:34 +0000

No problem Alain, glad to help.