window-scroll-functions and performance

[Antoine Levitt]

Hi,

I'm trying to track down the cause of performance issues in erc. One
problem is with erc-scroll-to-bottom. Here's a simple test: emacs -Q,
M-x erc, accept the default, M-x erc-scrolltobottom-mode, C-l to force
scrolltobottom to act, M-x elp-instrument-package erc, press and
maintain "a" for a while, then M-x elp-results. erc-scrolltobottom gets
called a lot, and that causes noticeable slowdowns: display doesn't keep
up with input, and CPU consumption jumps. This gets my emacs to 100% CPU
just inserting text.

Is it normal that window-scroll-functions gets called this much? Any
idea on how to improve scrolltobottom?