bug#38407: 27.0.50; infinite loop with display of large file without newlines

[Pieter van Oostrum]

Eli Zaretskii wrote:

 > > Date: Thu, 28 Nov 2019 19:30:50 +0100
 > > From: Pieter van Oostrum <pieter@vanoostrum.org>
 > > Cc: psainty@orcon.net.nz,
 > >     38407@debbugs.gnu.org
 > > 
 > > In Emacs 26, it is also slow, but the redisplay comes to an end, so I see 
 > > this as a kind of regression. The timing with Emacs 26 is very similar to 
 > > that in Emacs 27, except that it doesn't hang at the end. So my impression 
 > > is that the real difference is when the scrolling reaches the end of the 
 > > file. That also happens with M-> (end-of-buffer), which hangs indefinitely 
 > > (or at least a long time that is virtually indistinguishable from 
 > > indefinitely) in Emacs 27, but it does finish in Emacs 26.
 > 
 > I don't think there's any difference in this aspect between Emacs 26
 > and 27.  I see the same problem in both, FWIW, and I definitely didn't
 > wait for hours for redisplay to finish, let alone saw it "hang
 > indefinitely", even in an unoptimized build of Emacs 27 on a very slow
 > machine.  In my case it took something like 15 minutes.  I don't
 > understand why you see such long times.  Of course, I tried this with
 > a different JSON file than you did, so maybe there's something in your
 > file that causes even more slowdown.
 > 
 > In any case, try the latest master after setting bidi-inhibit-bpa to
 > non-nil.  In my testing, this is as fast as Emacs 23, i.e. no bidi
 > reordering at all, give or take some 10%.
 > 
 > And if you want the fastest display possible, use Fundamental mode,
 > not Text.
 > 
 > 
I have tried the latest version with so-long-mode, bidi-inhibit-bpa set to t, 
and the json file. Still hanging for a long time. Maybe it makes a difference 
that I am on MacOS?
-- 
Pieter van Oostrum <pieter@vanoostrum.org>
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]