tmux slow to interrupt process with Ctrl-C

Solution 1:

tmux now has the following options:

c0-change-interval interval
c0-change-trigger trigger

You can set values for these, which will make ^C and friends easier to type. See man tmux:

These two options configure a simple form of rate limiting for a pane. If tmux sees more than trigger C0 sequences that modify the screen (for example, carriage returns, linefeeds or backspaces) in one millisecond, it will stop updating the pane immediately and instead redraw it entirely every interval milliseconds. This helps to prevent fast output (such as yes(1)) overwhelming the terminal. The default is a trigger of 250 and an interval of 100. A trigger of zero disables the rate limiting.

Solution 2:

You can always issue kill-pane command from within the session. If the terminal text looks like garbage renaming the window and/or issuing reset should fix it.