 <p>Flymake sets a 1-second timer for each buffer that has flymake-mode enabled, to check to see if the buffer has been modified more than <code>flymake-no-changes-timeout</code> seconds ago.</p> <p>If you have a lot of buffers open (several hundred) in flymake-mode then this can devour a surprisingly large amount of CPU, I've a patched version of flymake that has a single global timer which fixes this, and a few other issues: <a href="https://github.com/illusori/emacs-flymake">https://github.com/illusori/emacs-flymake</a></p> <p>This might not be the same issue for you, but for me it would lock Emacs up when opening in desktop-mode with 600 files open, I'd be lucky to get one keypress processed every 15 minutes.</p>