Hi, I am trying notmuch + notmuch-emacs version 0.23.5-1~bpo8+1 from debian jessie backports, and reproduced this issue with both emacs 24.4 (jessie) and 24.5+1-6~bpo8+1 (jessie backports). When I make a query that gives many results (e.g. "review", which hits ~2200 emails with my Gerrit reviews) and want to display them in Tree View, the CPU usage stays high for several seconds. While this happens, the Emacs window flickers, like it was busy with redisplaying the buffer. If I pull the horizontal scroll of the Emacs buffer down, I can see that the buffer grows (like messages being inserted there). The Emacs profiler says that more than 50% of CPU time is spend in notmuch-tree-insert-forest-thread. Interestingly, the in the non-tree view the same query is processed in no time. Any idea? -- Piotr Trojanek