Re: on a buffer performance test on Windows GNU EMACS 28, 27, 26 and 24

[Eli Zaretskii]

> Date: Tue, 25 Aug 2020 00:35:50 -0300
> From: Wayne Harris via "Emacs development discussions." <emacs-devel@gnu.org>
> 
> On Windows, I said M-x run-python, then said
> 
>   for i in range(100000): print(i)
> 
> on both GNU EMACS 28, 27, 26 and GNU EMACS 24.  It turns out GNU EMACS
> 24 is the slowest.  There doesn't seem to be a difference between 28 and
> 27, but 26 is clearly slower too.
> 
> I timed the speed of the buffer to scroll up.  I used my own phone's
> stop watch.  I started out the slow one first, which was EMACS 24, only
> after it was running I started the clock, then I started GNU EMACS 28's
> code.  The result was GNU EMACS 28 finishes in less than 8.00 seconds.
> GNU EMACS 24 finishes after 24.44 seconds.  I didn't time 27 and 26, but
> I couldn't tell any difference between 28 and 27.  And 26 was slower
> than 27 and 28.
> 
> What is the reason for the difference?  Thanks!

We changed the value of w32-pipe-read-delay to zero in Emacs 27,
that sounds like the likely reason.