GNU bug report logs - #64391
30.0.50; buffer narrowing slowdown regression in emacs 29

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Message #11 received at 64391 <at> debbugs.gnu.org (full text, mbox):

From: Andrew Cohen <acohen <at> ust.hk>
To: 64391 <at> debbugs.gnu.org
Cc: Mattias Engdegård <mattiase <at> acm.org>,
 Gregory Heytings <gregory <at> heytings.org>
Subject: more info
Date: Sat, 01 Jul 2023 12:59:20 +0800

Mattias had flagged this code at line 2948 in editfns.c as a likely culprit. 

/* Record the accessible range of the buffer when narrow-to-region
     is called, that is, before applying the narrowing.  That
     information is used only by internal--label-restriction.  */
  Fset (Qoutermost_restriction, list3 (Qoutermost_restriction,
				       Fpoint_min_marker (),
				       Fpoint_max_marker ()));

Just for fun I simply commented it out (since the test code doesn't use
labeled restrictions) and ran the test code, and the problem disappears:

Emacs 30.0.50
Modify after narrowing:  0.076 s elapsed, 0 GCs, 0.000 s GC, 0.076 s non-GC
Modify before narrowing: 0.070 s elapsed, 0 GCs, 0.000 s GC, 0.070 s non-GC
-- 
Andrew Cohen

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