Re: Is Emacs buffer scroll/redisplay slow?

[Fabrice Popineau <fabrice.popineau@gmail.com>]

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Le dim. 19 janv. 2020 à 17:02, Eli Zaretskii <eliz@gnu.org> a écrit :

>
> > We could expect emacs to be a little bit more reactive here.
>
> Please repeat the experiment in a fresh "emacs -Q" right after
> starting it, then, after you finish scrolling, see what is the amount
> of CPU time reported by utilities such as PsList.  Alternatively, look
> at the load average value displayed by another Emacs session.
>
> In my testing, when I lean on the DOWN arrow, the system load never
> raises above 0.25, which means 3/4th of the time Emacs is idle.  My
> keyboard's auto-repeat rate is 30 characters per second, which means
> Emacs uses up about 7 msec (1000 / 30 / 4) to process every DOWN-arrow
> keypress, and that includes all the redisplay code, JIT font-lock
> etc.  I'm not sure I agree to call this "slow".
>

Ok, thanks for the explanation which makes sense. I was afraid that elisp
be a drag here,
but it does not seem to account for too much. And it is on par with other
code editors (I tried
PyCharm to compare)

(BTW, my keyboard is also on the fastest auto-repeat setting ... but there
are ways to speed it
 over the limit imposed by the control panel of windows)

Fabrice

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