bug#21028: Performance regression in revision af1a69f4d17a482c359d98c00ef86fac835b5fac (Apr 2014).

[Clément Pit--Claudel]

On 2016-12-19 11:58, Eli Zaretskii wrote:
> Also, do you see the slow-down when just displaying characters from
> this font, or only in the prettify-symbols mode?

Displaying symbols from that font is enough.  Given this, here's an updated 
recipe:

    /build/emacs/25/src/emacs -Q -l 21028.fixed.el 21028.fixed

Things are actually smoother using :family and :registry, but they are still 
unusable.  The problem is especially visible with vertical scrolling.

Here is a concrete experiment:

# With :name
$ time /build/emacs/25/src/emacs -Q -l 21028.el 21028.fixed --eval 
"(run-with-idle-timer 0 0 (lambda () (forward-line 25) (redisplay) 
(run-with-idle-timer 0 0 'kill-emacs)))"

real    0m3.500s
user    0m1.400s
sys     0m0.824s


# With :family and :registry
$ time /build/emacs/25/src/emacs -Q -l 21028.fixed.el 21028.fixed --eval 
"(run-with-idle-timer 0 0 (lambda () (forward-line 25) (redisplay) 
(run-with-idle-timer 0 0 'kill-emacs)))"

real    0m1.487s
user    0m0.752s
sys     0m0.188s


# With your patch from last month applied and the original one reverted:
$ time /build/emacs/master/src/emacs -Q -l 21028.fixed.el 21028.fixed --eval 
"(run-with-idle-timer 0 0 (lambda () (forward-line 25) (redisplay) 
(run-with-idle-timer 0 0 'kill-emacs)))"

real    0m0.486s
user    0m0.236s
sys     0m0.028s

Cheers,
Clément.

21028.fixed
Description: Text document

21028.fixed.el
Description: Text Data

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