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Re: Low redisplay performance (23 regression)

From: David Reitter
Subject: Re: Low redisplay performance (23 regression)
Date: Thu, 30 Apr 2009 08:44:23 -0400

On Apr 30, 2009, at 1:05 AM, Chong Yidong wrote:

On further investigation, I found that the problem can be solved with a
relatively safe change to handle_face_prop, so that it tells
face_at_buffer_position what the base face id is rather than having
face_at_buffer_position recalculate it each time the redisplay loop
wants to display the next face (!).  I've checked in the fix.

Thanks.  Kudos to you and Yamamoto Mitsuharu for finding these problems.
In the case that I documented, I see a big speedup, so that's good.

I still see other performance problems.
This one is easier to reproduce, I hope:

Emacs -Q
open file (e.g., src/emacs.c)
(setq redisplay-dont-pause t)
Scroll down page-wise using PgDown  [about 3 seconds]

C-x 5 2, move frame to the right so that they're side-by-side
Switch back to first frame
Home, then scroll down page-wise using PgDown [about 5 seconds}

It seems to me that this slow-down happens when the same buffer is shown in another frame, but not if another buffer is shown.

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