Improving Caching Performance on a DreamHost VPS

I'm hosting a couple sites on a DreamHost VPS.

I've used .phprc to make this customization on xcache on one of my domains:


However, the stats message provided by W3 Total Cache indicate that only 3/36 queries were cached using xcache. I have W3 Total Cache setup to cache database, object, and page request using xcache.

Is there any way to optimize the xcache configuration to improve caching and performance on domains using xcache?