Why does Emacs seem to perform slowly under certain conditions?
In some situations, Emacs performance can degrade. The following sections discuss these situations, why they come about, and what you can do about them. Menu bar updates In 19.34 the menu bar is updated more often than it needs to be, and each update can be a time consuming process. If you are using a single frame, you will likely not notice this behavior; if you are using a number of frames, you might notice slow redisplay performance. Currently the only way of fixing this is to turn menu-bar-mode off (e.g., typing “M-x menu-bar-mode”, or invoking (menu-bar-mode nil)). For more background, see Andrew’s messages on the topic. Transient mark mode The use of transient mark mode can trigger the slow menu bar update performance described above. When the mark is set in transient mark mode, the menu bar is updated after every keystroke and command. Again, turning off menu-bar-mode is the only way to prevent the slow performance without recompiling Emacs with patches. Kim Storm
