tags: have a different cache file per filter level Currently whichever filter level asks for tags last will write the data on disk. This create massive issues when tags are read for "visible" and "unfiltered" on large and multi headed repository (like Mozilla central). See issue4550 for details Each filter level recomputes its own cache without direct collaboration but they all share the same 'hgtagsfnodes' cache. And that is where most of the time is spent.