I sometimes notice that Emacs freezes up when I press a key like d to delete (adding the tag:trashing) for a couple of seconds. It's hard to track down, but I believe that I run into a conflict with a cron job updating the notmuch database, and Emacs waits for the notmuch tag change command to finish, which waits for the cron job to finish.
Does that sound likely? How do y'all debug and improve this?
