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---+ Monitoring Virtuoso Memory Consumption

%TOC%

---++ What

Like any other process, Virtuoso consumes system resources, including memory.  Here we describe one way to monitor the memory consumption of a Virtuoso server instance.

---++ Why monitor memory consumption?

In a mission critical application, running 24/7, memory consumption should be fairly consistent when the server is in use. A server should not consume all system memory, which may result in it hanging or being terminated by the operating system.

---++ How to monitor Virtuoso's memory consumption

On a Linux or other Unix-like system, you can use a script like this, which we've called <code>memcheck-virtuoso.sh</code>, which checks the memory consumption directly at the process level:
<verbatim>
#!/bin/bash
# saved to /tmp/memcheck-virtuoso.sh

pid=$(pidof virtuoso-t);
log=/tmp/mem-trace-virtuoso.txt;

echo $(printf "%s   %s   %s" $(date +%FT%R) $(cat /proc/${pid}/status |grep VmSize) ${pid}) | tee -a ${log}
</verbatim>

This script outputs 3 columns:
   1 <code>date-timestamp</code>
   2 <code><nowiki>VmSize</nowiki></code>: the actual memsize of the Virtuoso instance  (from the <code>cat -> grep</code> for that process id)
   3 the process id (or <code>PID</code>) of the Virtuoso instance


Here is a sample:
<verbatim>
$ cat /tmp/memcheck-virtuoso.txt
2014-11-14T17:22   VmSize: 15724332kB   3974
2014-11-14T17:46   VmSize: 15874064kB   3974
2014-11-14T17:55   VmSize: 15874064kB   3974
2014-11-14T18:52   VmSize: 15878076kB   3974
2014-11-14T18:52   VmSize: 15878076kB   3974
2014-11-14T22:29   VmSize: 15878076kB   3974
2014-11-14T22:30   VmSize: 15878076kB   3974
2014-11-14T22:56   VmSize: 15878076kB   3974
2014-11-14T22:56   VmSize: 15878076kB   3974
2014-11-14T23:33   VmSize: 15878076kB   3974
2014-11-14T23:33   VmSize: 15878076kB   3974
2014-11-14T23:52   VmSize: 15878076kB   3974
2014-11-14T23:53   VmSize: 15878076kB   3974
$
</verbatim>

The script can be run manually as required.  It can also be set up as a cron job to run at a specified internal, e.g., 4 hours in the sample below:
<verbatim>
$ crontab -l |grep mem
0 */4 * * * /tmp/memcheck-virtuoso.sh
</verbatim>

---++ Also See

   * Technical discussion about [[http://locklessinc.com/articles/memory_usage/][Measuring Memory Usage]]