setting JVM heap size in 64bit JVM

[Sreeraj AV, módosítva 11 év-val korábban]

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, módosítva 11 év-val korábban]

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, módosítva 11 év-val korábban]

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

[Sreeraj AV, módosítva 11 év-val korábban]

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, módosítva 11 év-val korábban]

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;

JAVA_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;

 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=33100

[Mika Koivisto, módosítva 11 év-val korábban]

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?

[Sagar A Vyas, módosítva 11 év-val korábban]

Hi Mika,

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

Thanks,
Sagar Vyas

[Sreeraj AV, módosítva 11 év-val korábban]

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?

[Mika Koivisto, módosítva 11 év-val korábban]

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.

[Linus Sphinx, módosítva 11 év-val korábban]

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.

-XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled -XX:SurvivorRatio=20 -XX: ParallelGCThreads=8