commit https://github.com/vim/vim/commit/864293abb72d62604d8d6b458addfb43c14230c3 Author: Bram Moolenaar <Bram@vim.org> Date: Thu Jun 2 13:40:04 2016 +0200 patch 7.4.1871 Problem: Appending to the quickfix list while the quickfix window is open is very slow. Solution: Do not delete all the lines, only append the new ones. Avoid using a window while updating the list. (closes #841)