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Sreeraj AV
setting JVM heap size in 64bit JVM
July 12, 2012 6:56 AM
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Sreeraj AV

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Join Date: April 26, 2010

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Below is the system details. This server is dedicated to Liferay portal. I need to change the JVM heap size. Can anyone please tell me what is the optimal heap size i can provide for this particular JVM?

Processor: Intel(R) Xeon(R) CPU E5645 @ 2.40GHz , dual core- 64bit
Memory : 6GB
OS : Linux 64bit
Java : java version "1.6.0_21-ea" 64bit
Sagar A Vyas
RE: setting JVM heap size
July 12, 2012 3:14 AM
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Sagar A Vyas

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Posts: 655

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Sreeraj AV:
Below is the system details. This server is dedicated to Liferay portal. I need to change the JVM heap size. Can anyone please tell me what is the optimal heap size i can provide for this particular JVM?

Processor: Intel(R) Xeon(R) CPU E5645 @ 2.40GHz , dual core- 64bit
Memory : 6GB
OS : Linux 64bit
Java : java version "1.6.0_21-ea" 64bit


Hi Sreeraj,

You can edit setenv.sh located in "tomcat-New\tomcat-6.0.32\bin"

-Xmx1024m -XX:MaxPermSize=256m" change it to -Xmx1024m -XX:MaxPermSize=512m"

Hope this help.

Thanks,
Sagar Vyas
Chintan Akhani
RE: setting JVM heap size
July 12, 2012 4:46 AM
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Chintan Akhani

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As you have 6 GB memory allocated for liferay instance only, so you can increase heap size upto 4 GB.
Sreeraj AV
RE: setting JVM heap size
July 12, 2012 6:55 AM
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Sreeraj AV

Rank: Regular Member

Posts: 233

Join Date: April 26, 2010

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Chintan Akhani:
As you have 6 GB memory allocated for liferay instance only, so you can increase heap size upto 4 GB.




Thanks for your reply. How you are telling 4GB? is there any procedure or best practices to determine the heap size value? Can you please explain..
Linus Sphinx
RE: setting JVM heap size
July 12, 2012 11:31 AM
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Linus Sphinx

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I use apache bench or http_load if non-ssl to simulate a bunch of users banging on the site while monitoring the memory usage in jvisualvm remotely and adjust accordingly til I get the behavior desired.
Given your hardware I'd assume you'll need some resources for other apps like backup etc. and recommend for a starting point a setenv.sh of;
1JAVA_OPTS="$JAVA_OPTS -XX:NewSize=700m -XX:MaxNewSize=700m -Xms2560m -Xmx2560m -XX:MaxPermSize=512m -Dfile.encoding=UTF8 -Duser.timezone=GMT -Dorg.apache.catalina.loader.WebappClassLoader.ENABLE_CLEAR_REFERENCES=false -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled -XX:SurvivorRatio=20 -XX: ParallelGCThreads=8"

concatenate this to the above string to enable JMX;
1 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=33100
Mika Koivisto
RE: setting JVM heap size in 64bit JVM
July 12, 2012 2:04 PM
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Mika Koivisto

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Heap is not absolute amount of memory your java process will take. There's several factors and I've quite recently explained them in my blog post: Why is my java process taking more memory than I gave it?
Mika Koivisto
RE: setting JVM heap size in 64bit JVM
July 12, 2012 2:07 PM
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Mika Koivisto

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The maximum heap certainly isn't 4GB on a 64bit system. You can increase it well beyond that but doing so may adversely affect the performance of the application because of longer full garbage collection times.
Sagar A Vyas
RE: setting JVM heap size in 64bit JVM
July 13, 2012 12:39 AM
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Sagar A Vyas

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Hi Mika,

Good Sharing,
@Sreeraj : you can follow given formula.
(-Xmx) + (-XX:MaxPermSize) + numberofthreads * (-Xss) + Other mem

Thanks,
Sagar Vyas
Linus Sphinx
RE: setting JVM heap size in 64bit JVM
July 13, 2012 8:58 AM
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Linus Sphinx

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Mika Koivisto:
The maximum heap certainly isn't 4GB on a 64bit system. You can increase it well beyond that but doing so may adversely affect the performance of the application because of longer full garbage collection times.

Must have been thinking 32 bit, thank you. GC is also tunable.
1-XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled -XX:SurvivorRatio=20 -XX: ParallelGCThreads=8
Sreeraj AV
RE: setting JVM heap size in 64bit JVM
July 18, 2012 12:19 AM
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Sreeraj AV

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Posts: 233

Join Date: April 26, 2010

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Thanks Mika..

Mika Koivisto:
Heap is not absolute amount of memory your java process will take. There's several factors and I've quite recently explained them in my blog post: Why is my java process taking more memory than I gave it?