Optimal number of facet threads

Hi All, I am trying to use fcs method of faceting and set the facet thread count to 3 .But when I check the thread dump around 15 threads are visible for faceting. Do setting facet thread count to 3 open 3 thread for each segment? On what basis should we decide no facet threads? Thanks

Optimal number of facet threads

Hi All, I am trying to use fcs method of faceting and set the facet thread count to 3 .But when I check the thread dump around 15 threads are visible for faceting. Do setting facet thread count to 3 open 3 thread for each segment? On what basis should we decide no facet threads? Thanks Saurabh S