There is a host of settings that can be used for the purpose of tuning the performance of a Virtuoso database server and OntoWiki in general. Below is a short discussion of some of them.
GNU/Linux system performance
If running Virtuoso on GNU/Linux some general system parameters might be adjusted in order to boost performance. Some important parmameters are listed below.
vm.swappiness
This setting controls how aggressively the kernel swaps out unused memory blocks to disk. On many systems this setting will greatly influence the performance of Virtuoso.
Please see the Virtuoso Wiki and e.g. this blogpost for more information.
The following might be a good recommendation:
# /sbin/sysctl -w vm.swappiness=10
# echo vm.swappiness=10 >> /etc/sysctl.conf
Settings in virtuoso.ini
Settings for the Virtuoso server are generally done in the file virtuoso.ini. Note that settings in this file overrides settings done via the ‘Virtuoso Conductor’ web interface. Some settings of interest are discussed below. Please see this article, among other things.
SPARQL endpoint performance
Most notably the settings discussed here affect the SPARQL endpoint performance.
General Virtuoso RDF performance
The Virtuoso RDF performande is discussed here and here.
These articles deserve prudent reading, and the most prominent settings should be outlined herein.