Re: Is Emacs buffer scroll/redisplay slow?

[Alan Mackenzie]

Hello, Fabrice.

On Sun, Jan 19, 2020 at 10:34:07 +0100, Fabrice Popineau wrote:
> Hi,

> Out of curiosity, I timed 'emacs -Q' ....

Which version of Emacs?

> .... scrolling through an elisp buffer: I started the timer by hand and
> scrolled down for 1000 lines ....

How, exactly, did you do the scrolling?  How did you stop the scrolling
at 1000 lines?  Do you get this slowness on any elisp buffer, or is it a
particular one?

> .... and it took 45s on Windows/WSL and 35s on Windows/native.

That is slow indeed.

> This is on a pretty decent laptop (core i7, 32Gb ram, 4k display) I
> don't care about the difference here, but overall, I find it pretty
> slow. Is there something that could be done to enhance it?  What is the
> main bottleneck here?

Have you tried profiling this scrolling, yet?  If not, I suggest you do,
with M-x profiler-start <CR> <CR>, running the scrolling, then M-x
profiler-report.  In the report buffer, hit <CR> to get successively
deeper results.

This may well give you an idea where the slowness is happening.

> Best regards,

> Fabrice

-- 
Alan Mackenzie (Nuremberg, Germany).