Re: Low redisplay performance (23 regression)

[David Reitter]

On Apr 22, 2009, at 12:28 PM, Chong Yidong wrote:
> So, the slowdown may be related to displaying multiple faces?  I have
> not experienced anything like this, myself.  If you do M-x
> list-faces-display and scroll through that buffer, is there a  
> slowdown?
Yes, definitely, but if and only if face-remapping-alist is enabled  
(remapping the default face).
With the tabbar enabled, scrolling down that buffer takes about twice  
as long, depending on how many tabs I show.
Without the tabbar, I estimate the slowdown is about 20-30%.

> It's possible that tabbar is doing something with its face computation
> that is much more expensive on Emacs 23 than on Emacs 22; I don't have
> time to look at its code, however.

As above, it's not just the tabbar; doing something relatively simple  
with face-remapping-alist already shows the effect.
I've been working on coming up with a reproducible standalone  
example.  Perhaps, if the others who can reproduce, could attempt the  
same, we'd get somewhere.