bug#71644: 30.0.50; Severe slowdown in larger files with markers beginning in emacs 29+

[Ihor Radchenko <yantar92@posteo.net>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Yes, definitely.  The threshold is at about N/100 where N is the number
> of markers/headings.  But why 100?

Maybe because

bytepos - best_below_byte > 5000
and distance += BYTECHAR_DISTANCE_INCREMENT;
(BYTECHAR_DISTANCE_INCREMENT = 50)

Then, (/ 5000 50) ; -> 100.

In other words,
for (tail = BUF_MARKERS (b); tail; tail = tail->next)
loop is roughly bound to (min number-of-markers 100)-ish
repetitions. So, once the number of markers exceeds 100, there is no
more scaling with the marker number.

-- 
Ihor Radchenko // yantar92,
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