I ran into a case where this setting was very important. I ran my recommender app in Apache Tomcat and used precomputed item similarities that were held in memory (these occupied something like 2 or 3 GB if I recall correctly).
Tomcat (I used 5.5) ensures that each object is checked for GC at least once per hour to battle known memory leaks of some popular libraries. This stopped the JVM for several seconds each hour as lots of small objects had to be checked which resulted in a violation of the response time guarantees of the recommender. Disabling explicit GC stopped this behavior and full GC was only triggered, when the similarities are updated (which is perfectly ok). --sebastian On 14.12.2011 10:45, Aleksei Udatšnõi wrote: > I have noticed that in Mahout's wiki > (https://cwiki.apache.org/MAHOUT/recommender-documentation.html), it > is recommended to set JVM setting -XX:-DisableExplicitGC > > However in the book "Mahout in Action" Appendix A "JVM tuning" this > setting is not mentioned. > > Assuming, I use out-of-the-box Mahout item- and user-based > recommenders embedded into servlets. I wonder if Mahout authors still > recommend to use this setting for better performance? > > Thank you > Aleksei
