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High Tomcat's Java Virtual Memory above -Xmx setting?

Question asked by jonvargas on Oct 17, 2014
Latest reply on Oct 20, 2014 by jonvargas
Hi there,

We have a 3 years old Alfresco 4.2 server for around 500 casual users, with the following specs:

<strong>System:</strong>

* RAM: 32 GB
* CPU: 6 cores
* Arch: 64 bits
* OS: Ubuntu 12.04

<strong>Applications:</strong>

* Tomcat 7 (alfresco, share, solr)
* PostgreSQL

<strong>Resources usage:</strong>

As consumed by Tomcat's java process:

* Resident memory: 5.79 GB
* Virtual memory: 16.5 GB

<strong>JVM Tuning:</strong>

* Xms: 2 Gb
* Xmx: 12 Gb
* Perms: 512M

<strong>Questions:</strong>

* Why does the java process's virtual memory exceeds by 4.5 GB the configured Xmx value of the JVM? How it is possible and how can I take real control of the maximum reserved memory for it?

* For PostgreSQL, how much memory could be allocated for around 100 concurrents users? I've noticed that each PostgreSQL process takes around 130 MB of virtual memory

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