Bug: sys.dm_db_session_space_usage Reporting Extremely High Tempdb Allocations

A little more than a year ago while working at Idera, I was consulted on reports from a few clients using the Idera monitoring tool SQL diagnostic manager (SQLdm). SQLdm was reporting very high numbers for internal object allocations (internal_objects_alloc_page_count) and very low numbers for internal object deallocations (internal_objects_dealloc_page_count) to the point that SQLdm showed that individual sessions were reported using more space than was available in the database. I worked with Vicky Harp (blog|@vickyharp), SQLdm dev lead and an