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Performance asymmetry with overlays
From: |
Satyaki Das |
Subject: |
Performance asymmetry with overlays |
Date: |
Fri, 16 May 2003 16:10:13 -0700 |
There seems to be an asymmetry in performance when overlays are
used depending on initial cursor position in a buffer. Here is a
test that demonstrates it:
0. Save the attached file as overlay-test.el
1. Start emacs with:
emacs -q --no-site-file -l overlay-test.el
2. Open a large file. I tried this with the NEWS file by doing:
C-h n
3. Go to the end of the buffer (with M->) and do:
M-x overlay-test RET
It runs very quickly (on my 800MHz Pentium 3 it takes 0.22 sec)
4. Remove the overlays with: M-x overlay-test-reset.
5. Go to the beginning of the buffer and run overlay-test again.
This time it takes about 71.5 sec!
[I got the times by using elp]
I am running CVS Emacs from yesterday on a Redhat GNU/Linux 9.0
on a Pentium 3. I get similar results with Emacs-21.3.1 built on
the same machine. I also tried on a different Solaris machine
with Emacs-21.2 and got similar results.
I did profile overlay-test. It seems that when cursor is at top of
the buffer initially, make-overlay and forward-line both take much
longer than in the other case.
Can this be improved?
Thanks,
Satyaki
overlay-test.el
Description: Test for Overlays
- Performance asymmetry with overlays,
Satyaki Das <=