bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

[-- Attachment #1: Type: text/plain, Size: 7153 bytes --]

Hello.  I'm experiencing major slowdown in Emacs -q fundamental mode
when setting `mouse-wheel-progressive-speed' to `nil'.  Here are
reproduction steps:

1. Run emacs -q
2. Open some big file, in my case I've opened lisp-mode.el
3. Turn on fundamental-mode (optional)
4. Go to the end of the buffer.
5. Rapidly produce scroll up events from touchpad or mouse wheel
   (although it is much harder to achieve with mouse) with significant
   scroll amount.  By significant scroll amount I mean continuous
   scrolling event from touchpad, which can be achieved by swiping over
   whole touchpad area very rapidly.
6. Observe that Emacs doesn't scroll almost at all and just waits until
   scroll events will stop.  Then it scrolls correct amount.

The delay I'm talking about is what bothers me.

First, there's no delay at all when scrolling with scrollbars
(provided by `scroll-bar-mode').  I can scroll with scrollbars as
rapidly as I want, and there is literally no lag whatsoever.

Second, when producing slow scrolling motion on touchpad or mouse
(e.g. one line at a time) scrolling is very responsive.  But I'm
scrolling one line at a time very rarely so this is useless to me.

Third, this bug also reproduces with default value of
`mouse-wheel-progressive-speed', although it is a bit more difficult
to catch this as it requires enormously big buffer for lag to build
up, as scrolling increases in speed (seemingly) exponentially and can
reach top of the buffer before lag builds up significantly.

Last but not least, this also happens when scrolling down (to buffer
end) but the lag seems to be smaller, yet it still noticeable.

I've did some profiling during irresponsibility the amount of CPU
samples is enormous, but down the tree, called functions don't consume
much.  Here's a fragment of report, and I've also attached profiler
exported report to the mail:

        4400  88% - command-execute
        4359  87%  - funcall-interactively
        3776  75%   - mwheel-scroll
          26   0%      mouse-wheel--get-scroll-window
          26   0%    - run-with-timer
          23   0%     - run-at-time
           4   0%        timer-set-time
           1   0%        timer-set-function
           1   0%        timer-activate
          23   0%    - scroll-up
          12   0%     - eval
           8   0%      - if
           1   0%         display-graphic-p
           1   0%        mode-line-eol-desc
          19   0%    - scroll-down
           9   0%     - eval
           7   0%      - if
           1   0%         frame-parameter
           1   0%        unless
          15   0%    - error-message-string
          11   0%     - substitute-command-keys
           7   0%      - #<compiled -0x1fc708cc6b8a9a73>
           4   0%       - kill-buffer
           2   0%        - replace-buffer-in-windows
           1   0%         - unrecord-window-buffer
           1   0%            assq-delete-all
           2   0%      #<compiled -0xd2dd66c27d231f8>
           1   0%      message
         288   5%   - scroll-bar-toolkit-scroll
         264   5%    - sit-for
          10   0%     - redisplay_internal (C function)
           2   0%      - eval
           1   0%         mode-line-eol-desc
           1   0%         if

My wild guess is that touchpad sends much more input to Emacs, compared
to mouse, and that's why scrolling function has to work with much more
inputs and hence the struggle.  I was under assumption that Emacs'
font-lock was the culprit here, as disabling it kinda helps, but then
I've managed to reproduce it without font locking and now I think that
there might be another issue.  Everything I've tested happened on GCC
Emacs branch, but also happens (and actually a bit more noticeable in
27.1 and master branches).


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
3.24.13, cairo version 1.16.0)
 of 2021-01-17 built on toolbox
Repository revision: 88100bed0af530f04cf56acca9f9d1bb12b45771
Repository branch: feature/native-comp
Windowing system distributor 'Fedora Project', version 11.0.12010000
System Description: Fedora 33 (Workstation Edition)

Configured using:
 'configure --with-nativecomp --with-mailutils
 --prefix=/home/andreyorst/.local/emacs
 --bindir=/home/andreyorst/.local/bin
 '--program-transform-name=s/^ctags$/ctags.emacs/''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY
INOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE
XIM XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source eieio eieio-core eieio-loaddefs
password-cache json map mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils jka-compr shortdoc text-property-search
cl-indent comp comp-cstr warnings rx cl-seq cl-macs cl-extra seq
byte-opt gv bytecomp byte-compile cconv inf-lisp comint ansi-color ring
thingatpt profiler help-fns radix-tree cl-print debug backtrace
help-mode find-func time-date subr-x vc-git diff-mode easymenu
easy-mmode cl-loaddefs cl-lib iso-transl tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice button
loaddefs faces cus-face pcase macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process nativecomp
emacs)

Memory information:
((conses 16 120435 14545)
 (symbols 48 9569 1)
 (strings 32 28965 2841)
 (string-bytes 1 952843)
 (vectors 16 38276)
 (vector-slots 8 804855 15451)
 (floats 8 80 204)
 (intervals 56 3638 189)
 (buffers 984 12))


-- 
Best regards,
Andrey Listopadov

[-- Attachment #2: report --]
[-- Type: application/octet-stream, Size: 12439 bytes --]


[profiler-profile "28.1" cpu #s(hash-table size 97 test equal rehash-size 1.5 rehash-threshold 0.8125 data ([profiler-report-insert-calltree-children profiler-report-render-calltree-1 profiler-report-rerender-calltree profiler-report-render-calltree profiler-report-setup-buffer profiler-report-profile-other-window profiler-report-cpu profiler-report eval-expression funcall-interactively command-execute nil nil nil nil nil] 1 [display-buffer-pop-up-window display-buffer--maybe-pop-up-window display-buffer--maybe-pop-up-frame-or-window display-buffer pop-to-buffer switch-to-buffer-other-window profiler-report-profile-other-window profiler-report-cpu profiler-report eval-expression funcall-interactively command-execute nil nil nil nil] 6 [nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 6539 [redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 37 [timer-activate timer-event-handler nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 3664 [mouse-wheel--get-scroll-window mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 26 [eval redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 3 [scroll-up mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 11 [if eval redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil] 23 [run-at-time run-with-timer mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 17 [keymap-canonicalize redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 3 ["#<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_10>" apply timer-event-handler nil nil nil nil nil nil nil nil nil nil nil nil nil] 3 [eval scroll-down mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 1 ["#<compiled -0xd2dd66c27d231f8>" mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 2 ["#<compiled 0x6607ab7520a98b4>" redisplay--update-region-highlight run-hook-with-args redisplay--pre-redisplay-functions apply "#<compiled 0x1342edd5b5745bef>" redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil] 4 [window-pixel-edges window-at-side-p mode-line-default-help-echo redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil] 5 [scroll-down mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 10 [if eval scroll-up mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 7 [tool-bar-make-keymap-1 tool-bar-make-keymap redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil] 3 [redisplay--update-region-highlight run-hook-with-args redisplay--pre-redisplay-functions apply "#<compiled 0x1342edd5b5745bef>" redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil] 1 [frame-parameter if eval scroll-down mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 1 [internal-timer-start-idle nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 2 [run-at-time run-with-timer blink-cursor--start-timer blink-cursor-start apply timer-event-handler nil nil nil nil nil nil nil nil nil nil] 1 [mode-line-eol-desc eval scroll-up mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [kill-this-buffer-enabled-p redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 2 [mwheel-filter-click-events nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [if eval scroll-down mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 6 [eval scroll-up mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 3 ["#<compiled -0x407f9bd5497621a>" internal-echo-keystrokes-prefix nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [undo-auto--add-boundary nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [timer-set-function run-at-time run-with-timer mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 6 [timer-set-time run-at-time run-with-timer mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 4 [timer-inc-time timer-event-handler nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [tooltip-show-help nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [run-with-idle-timer blink-cursor--start-idle-timer blink-cursor-check blink-cursor--rescan-frames apply "#<compiled 0x1bc2eb6ca99c6a39>" handle-focus-in funcall-interactively command-execute nil nil nil nil nil nil nil] 1 [mode-line-default-help-echo redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 2 [mwheel-inhibit-click-timeout apply timer-event-handler nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [mouse--click-1-maybe-follows-link nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 254 [window-at-side-p mode-line-default-help-echo redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 1 ["#<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_0>" internal--before-save-selected-window scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 1 [scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 21 [mode-line-eol-desc eval redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 1 [if eval redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 1 ["#<compiled 0x6607ab7520a98b4>" redisplay--update-region-highlight run-hook-with-args redisplay--pre-redisplay-functions apply "#<compiled 0x1342edd5b5745bef>" redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil] 1 [frames-on-display-list "#<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_0>" internal--before-save-selected-window scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 3 [message mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 1 ["#<compiled -0x1fc708cc6b8a9a73>" substitute-command-keys error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 3 [kill-buffer "#<compiled -0x1fc708d9ebea0673>" substitute-command-keys error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 2 [error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 4 [apply "#<compiled 0x1342edd5b5745bef>" redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil] 4 [substitute-command-keys error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 4 [replace-buffer-in-windows kill-buffer "#<compiled -0x1fc708cd2ece9a73>" substitute-command-keys error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil] 1 [mode-line-eol-desc eval redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil] 2 ["#<compiled -0x16886ce7ad90d52d>" apply gui-backend-selection-exists-p "#<compiled -0x4c2f306cc48bdb5>" funcall redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil] 1 [internal-echo-keystrokes-prefix nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 4 [timer-activate run-at-time run-with-timer mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [window-at-side-p mode-line-default-help-echo redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [tooltip-show tooltip-help-tips tooltip-timeout apply timer-event-handler nil nil nil nil nil nil nil nil nil nil nil] 1 [x-show-tip tooltip-show tooltip-help-tips tooltip-timeout apply timer-event-handler nil nil nil nil nil nil nil nil nil nil] 1 [tool-bar-make-keymap redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 ["#<compiled 0x1fcc7f61ec2e2>" scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 1 ["#<compiled -0x16886ce7ad90d52d>" apply gui-backend-selection-exists-p "#<compiled -0x4c2f306cc48bdb5>" funcall redisplay_internal\ \(C\ function\) sit-for scroll-bar-toolkit-scroll funcall-interactively command-execute nil nil nil nil nil nil] 2 [run-with-timer mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 3 [run-hook-with-args redisplay--pre-redisplay-functions apply "#<compiled 0x1342edd5b5745bef>" redisplay_internal\ \(C\ function\) nil nil nil nil nil nil nil nil nil nil nil] 4 [timer-event-handler nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [save-buffers-kill-emacs handle-delete-frame funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil] 6 [save-some-buffers save-buffers-kill-emacs handle-delete-frame funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil] 133 ["#<compiled 0x1f40d722227a>" save-some-buffers save-buffers-kill-emacs handle-delete-frame funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [handle-delete-frame funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 134 [eval redisplay_internal\ \(C\ function\) save-buffers-kill-emacs handle-delete-frame funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [handle-focus-out funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [timer-set-idle-time run-with-idle-timer blink-cursor--start-idle-timer blink-cursor-check blink-cursor--rescan-frames apply "#<compiled 0x1bc2eb6ca99c6a39>" handle-focus-in funcall-interactively command-execute nil nil nil nil nil nil] 1 [undo-auto--boundaries undo-auto--add-boundary nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 1 [unless eval scroll-down mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil] 1 [assq-delete-all unrecord-window-buffer replace-buffer-in-windows kill-buffer "#<compiled -0x1fc708da2f9d3e73>" substitute-command-keys error-message-string mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil] 1 [display-graphic-p if eval scroll-up mwheel-scroll funcall-interactively command-execute nil nil nil nil nil nil nil nil nil] 1 [byte-code command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil nil] 19 [font-lock-mode turn-on-font-lock turn-on-font-lock-if-desired global-font-lock-mode-enable-in-buffers run-hooks run-mode-hooks minibuffer-inactive-mode read--expression byte-code command-execute nil nil nil nil nil nil] 1 [read--expression byte-code command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 20 [funcall-interactively command-execute read--expression byte-code command-execute nil nil nil nil nil nil nil nil nil nil nil] 1 [eval-expression funcall-interactively command-execute nil nil nil nil nil nil nil nil nil nil nil nil nil] 4 [Automatic\ GC] 475)) (24606 51417 254368 662000) nil]

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sat, 6 Feb 2021 20:33:56 +0300
> 
> 1. Run emacs -q
> 2. Open some big file, in my case I've opened lisp-mode.el
> 3. Turn on fundamental-mode (optional)
> 4. Go to the end of the buffer.
> 5. Rapidly produce scroll up events from touchpad or mouse wheel
>    (although it is much harder to achieve with mouse) with significant
>    scroll amount.  By significant scroll amount I mean continuous
>    scrolling event from touchpad, which can be achieved by swiping over
>    whole touchpad area very rapidly.
> 6. Observe that Emacs doesn't scroll almost at all and just waits until
>    scroll events will stop.  Then it scrolls correct amount.
> 
> The delay I'm talking about is what bothers me.

I cannot reproduce this.  Did you try "emacs -Q"?

Please load mwheel.el (NOT the .elc file!), and then profile the slow
scrolling again and show a fully-expanded profile.  That might help us
understand what part of mwheel-scroll takes the lion's share of CPU
cycles.

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

[-- Attachment #1: Type: text/plain, Size: 6697 bytes --]

On Sat, Feb 6, 2021 at 8:59 PM Eli Zaretskii <eliz@gnu.org> wrote:

> I cannot reproduce this.  Did you try "emacs -Q"?

Yes, the behavior I've described happens to me in emacs -Q (and emacs -q)

> Please load mwheel.el (NOT the .elc file!), and then profile the slow
> scrolling again and show a fully-expanded profile.  That might help us
> understand what part of mwheel-scroll takes the lion's share of CPU
> cycles.

Here's whole report expanded (btw can't find if there's expand-all
feature?):

       11593  91% - command-execute
       11549  91%  - funcall-interactively
       11542  91%   - mwheel-scroll
       11536  91%    - let*
       11420  90%     - condition-case
       11381  90%      - unwind-protect
       11377  90%       - let
       11373  90%        - cond
       11372  90%         - condition-case
       10868  86%          - funcall
         324   2%           - scroll-down
         263   2%            - jit-lock-function
         255   2%             - jit-lock-fontify-now
         235   1%              - jit-lock--run-functions
         233   1%               - #<compiled -0x152f649d2893cb7b>
         232   1%                - font-lock-fontify-region
         224   1%                 - font-lock-default-fontify-region
         132   1%                  - font-lock-fontify-syntactically-region
         110   0%                     syntax-ppss
          10   0%                   - lisp-font-lock-syntactic-face-function
           7   0%                    - lisp-string-in-doc-position-p
           1   0%                       forward-sexp
           2   0%                    - lisp-string-after-doc-keyword-p
           2   0%                     - backward-sexp
           2   0%                        forward-sexp
          35   0%                  - font-lock-fontify-keywords-region
          17   0%                   - lisp--el-match-keyword
           2   0%                    - lisp--el-non-funcall-position-p
           1   0%                       syntax-ppss
           5   0%                     #<compiled -0x4e6368f210a40dc>
           1   0%                   - let
           1   0%                    - cond
           1   0%                       eq
           1   0%                     font-lock-prepend-text-property
           1   0%
lisp--match-confusable-symbol-character
           6   0%                    font-lock-unfontify-region
          24   0%            - eval
          18   0%             - if
           3   0%                display-graphic-p
           2   0%             - unless
           1   0%                if
           1   0%               mode-line-eol-desc
         502   3%          - unwind-protect
         502   3%           - funcall
           5   0%            - scroll-down
           4   0%             - eval
           4   0%                if
           4   0%       - if
           2   0%          if
           6   0%      - message
           4   0%       - error-message-string
           3   0%        - substitute-command-keys
           1   0%           #<compiled -0x1fc73df3077c5a73>
           1   0%         clear-minibuffer-message
          57   0%     - if
          50   0%      - progn
          46   0%       - setq
          39   0%        - run-with-timer
          33   0%         - run-at-time
           4   0%          - timer-set-time
           1   0%             timer--time-setter
           1   0%            timer-activate
           3   0%          *
           2   0%         if
           3   0%      - let
           2   0%       - while
           1   0%        - consp
           1   0%         - setq
           1   0%            car-safe
          49   0%     - mouse-wheel--get-scroll-window
          48   0%      - or
          47   0%       - catch
          45   0%        - let*
          44   0%         - if
          39   0%            progn
           4   0%            mwheel-event-window
           1   0%     - delq
           1   0%      - delq
           1   0%         delq
           5   0%   - eval-expression
           5   0%      progn
          42   0%  - byte-code
          29   0%   - read--expression
           2   0%    - redisplay_internal (C function)
           2   0%     - funcall
           2   0%      - #<compiled 0x4f9dac7e18824a>
           2   0%       - gui-backend-selection-exists-p
           2   0%        - apply
           2   0%           #<compiled -0x16887ad6f3ef152d>
           1   0%    - frame-windows-min-size
           1   0%       window-min-size
         976   7% - ...
         976   7%    Automatic GC
          13   0% - timer-event-handler
          13   0%  - apply
          13   0%   - #<subr
F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_11>
          13   0%    - eldoc-print-current-symbol-info
          13   0%     - eldoc--invoke-strategy
          13   0%      - eldoc-documentation-default
          13   0%       - elisp-eldoc-funcall
          13   0%        - elisp--fnsym-in-current-sexp
          13   0%         - elisp--beginning-of-sexp
          13   0%          - forward-sexp
           4   0%           - scan-sexps
           4   0%              syntax-ppss
          11   0% - jit-lock--antiblink-post-command
          11   0%    syntax-ppss
           5   0% - undo-auto--add-boundary
           4   0%  - undo-auto--boundaries
           2   0%     undo-auto--ensure-boundary
           3   0% - mwheel-filter-click-events
           2   0%  - if
           2   0%     eq
           3   0%   internal-timer-start-idle
           3   0%   tooltip-hide
           2   0% - redisplay_internal (C function)
           1   0%  - funcall
           1   0%   - #<compiled 0x4f9dac7e18824a>
           1   0%    - gui-backend-selection-exists-p
           1   0%     - apply
           1   0%        #<compiled -0x16887ad6f3ef152d>
           1   0%  - jit-lock-function
           1   0%   - jit-lock-fontify-now
           1   0%    - jit-lock--run-functions
           1   0%     - #<compiled -0x152f64ab9864c87b>
           1   0%      - font-lock-fontify-region
           1   0%       - font-lock-default-fontify-region
           1   0%        - font-lock-fontify-syntactically-region
           1   0%           syntax-ppss
           2   0% - #<compiled 0x1cf15f5a0be052d1>
           1   0%  - filter-buffer-substring
           1   0%   - buffer-substring--filter
           1   0%    - #<compiled 0x1f88987120b96adb>
           1   0%       apply

Also, I've attached a video of what I'm doing.

 VID_20210206_211819.tar.xz
<https://drive.google.com/file/d/19dsfdY_f30FKRTGJld28wuBcJB0T8LrT/view?usp=drive_web>

-- 
Best regards,
Andrey Listopadov

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

On Sat, Feb 6, 2021 at 9:34 PM Andrey Orst <andreyorst@gmail.com> wrote:
>
> On Sat, Feb 6, 2021 at 8:59 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > I cannot reproduce this.  Did you try "emacs -Q"?
>
> Yes, the behavior I've described happens to me in emacs -Q (and emacs -q)

I should mention again, that I'm setting
`mouse-wheel-progressive-speed' to `nil' after I'm opening emacs -Q.
Without this setting the lag still there, but it is a bit harder to
capture it in -Q mode, as buffer scrolls to upper boundary almost
instantly with that much speed produced by toucpad. With my regular
configuration the value of this variable doesn't matter.

-- 
Best regards,
Andrey Listopadov

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sat, 6 Feb 2021 21:34:29 +0300
> Cc: 46350@debbugs.gnu.org
> 
> > Please load mwheel.el (NOT the .elc file!), and then profile the slow
> > scrolling again and show a fully-expanded profile.  That might help us
> > understand what part of mwheel-scroll takes the lion's share of CPU
> > cycles.
> 
> Here's whole report expanded (btw can't find if there's expand-all feature?):

Yes, "C-u RET".

>        11593  91% - command-execute
>        11549  91%  - funcall-interactively
>        11542  91%   - mwheel-scroll
>        11536  91%    - let*
>        11420  90%     - condition-case
>        11381  90%      - unwind-protect
>        11377  90%       - let
>        11373  90%        - cond
>        11372  90%         - condition-case
>        10868  86%          - funcall
>          324   2%           - scroll-down
>          263   2%            - jit-lock-function
>          255   2%             - jit-lock-fontify-now
>          235   1%              - jit-lock--run-functions

I cannot make sense out of this: this profile says that funcall takes
most of the time, and the function it calls, scroll-down, takes almost
no time?  Does anyone have any idea what could be going on here?

If this is just some artifact of "M-x profile", and most of the time
is spent in scroll-down, then I'm not sure what can be done, nor why
you see something I don't.  Do you use a large frame and/or a small
font?  And how many mouse-wheel events Emacs receives in your
scenario, anyway?

Oh, and what happens if you raise gc-cons-threshold to a large value?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sat, 6 Feb 2021 21:55:58 +0300
> Cc: 46350@debbugs.gnu.org
> 
> I should mention again, that I'm setting
> `mouse-wheel-progressive-speed' to `nil' after I'm opening emacs -Q.

Yes, I tried that.  I don't see anything abnormal except the slower
scrolling (which is expected without the progressive-speed setting).

> Without this setting the lag still there, but it is a bit harder to
> capture it in -Q mode, as buffer scrolls to upper boundary almost
> instantly with that much speed produced by toucpad.

What is the size of the buffer that it scrolls almost instantly to
BOB?  How many lines?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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>
> Do you use a large frame and/or a small
> font?


In fact, yes, my screen is 2K, and system font scaling is set to 1.44, but
this also happens on regular 1080p screen with regularly sized font.

And how many mouse-wheel events Emacs receives in your
> scenario, anyway?
>

Sorry, how can I check that? I do think that Emacs actually receives a
metric ton of events, as scolling with mouse seems hardly lag at all, and
scrolling in termux with touch events also not as laggy.

Oh, and what happens if you raise gc-cons-threshold to a large value?
>

No difference. Note, that scrolling with scrollbars has no lag at all, so I
don't think that GC is relevant here.

I've also noticed that scrollin with scrollbar has (sit-for 0) in the body
of the scroll function, and IIRC mwheel-scroll doesnt sit at all. maybe
because of that it consumes too many inputs?

I wonder if you could send tons of scrolling inputs via xdotool or smth
like that on Linux?

>

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sat, 6 Feb 2021 22:47:55 +0300
> Cc: 46350@debbugs.gnu.org
> 
>  And how many mouse-wheel events Emacs receives in your
>  scenario, anyway?
> 
> Sorry, how can I check that?

Add a call to 'message' to mwheel-scroll, and have it show a counter
that counts up?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

On Sat, Feb 6, 2021 at 11:03 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> >  And how many mouse-wheel events Emacs receives in your
> >  scenario, anyway?
> >
> > Sorry, how can I check that?
>
> Add a call to 'message' to mwheel-scroll, and have it show a counter
> that counts up?

I've did as you've suggested. When scrolling buffer of 1405 lines from
bottom to the top (while emacs is unresponsive) mwheel-scroll function
seems to be called about ~1351 times. Single fast flick over touchpad
produces ~40 calls to mwheel-scroll.
Adding (sit-for 0) at the start of the function doesn't have any effect.

> What is the size of the buffer that it scrolls almost instantly to
> BOB?  How many lines?

1405 lines. I'm testing this on bundled lisp-mode.el

-- 
Best regards,
Andrey Listopadov

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sun, 7 Feb 2021 20:23:09 +0300
> Cc: 46350@debbugs.gnu.org
> 
> > Add a call to 'message' to mwheel-scroll, and have it show a counter
> > that counts up?
> 
> I've did as you've suggested. When scrolling buffer of 1405 lines from
> bottom to the top (while emacs is unresponsive) mwheel-scroll function
> seems to be called about ~1351 times. Single fast flick over touchpad
> produces ~40 calls to mwheel-scroll.

1350 calls during what time, approximately? less than a second?

I don't think Emacs can scroll so fast, one line at a time.  Note that
when you scroll with the scroll-bar, Emacs doesn't call
scroll-up/down, it just goes to a suitably calculated buffer position.
Which is why scroll-bar scrolling is much faster.  But I don't see how
we can do something similar with the mouse-wheel, since it doesn't
allow to calculate the buffer position to go to; Emacs needs to do
that calculation itself, and that what makes the scrolling so much
slower.

> > What is the size of the buffer that it scrolls almost instantly to
> > BOB?  How many lines?
> 
> 1405 lines. I'm testing this on bundled lisp-mode.el

Which explains why it scrolls in one go: 1405 ≅ 1350.

So, once we've established that the touchpad injects 1-line scroll
requests at such a high rate, what else needs to be investigated here?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

On Sun, Feb 7, 2021 at 8:49 PM Eli Zaretskii <eliz@gnu.org> wrote:
> 1350 calls during what time, approximately? less than a second?

If you've watched the video I've linked you can get a sense of what
time it takes -- about 15 seconds. Or more if I continue swyping
rapidly, since Emacs just sits at the bottom eating all input until I
stop.
Touchpad generates about 20-30 inputs per swipe, so I think ~90 inputs
is maximum human can produce in 1 second

> I don't think Emacs can scroll so fast, one line at a time.  Note that
> when you scroll with the scroll-bar, Emacs doesn't call
> scroll-up/down, it just goes to a suitably calculated buffer position.
> Which is why scroll-bar scrolling is much faster.  But I don't see how
> we can do something similar with the mouse-wheel, since it doesn't
> allow to calculate the buffer position to go to; Emacs needs to do
> that calculation itself, and that what makes the scrolling so much
> slower.

Can Emacs poll mouse events less frequently? Maybe some libinput stuff
needs tweaking?

> > > What is the size of the buffer that it scrolls almost instantly to
> > > BOB?  How many lines?
> >
> > 1405 lines. I'm testing this on bundled lisp-mode.el
>
> Which explains why it scrolls in one go: 1405 ≅ 1350.
>
> So, once we've established that the touchpad injects 1-line scroll
> requests at such a high rate, what else needs to be investigated here?

There I was talking about progressive speed turned on, as it builds up
almost instantly with my touchpad producing 30 inputs per swipe.


-- 
Best regards,
Andrey Listopadov

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sun, 7 Feb 2021 21:33:25 +0300
> Cc: 46350@debbugs.gnu.org
> 
> On Sun, Feb 7, 2021 at 8:49 PM Eli Zaretskii <eliz@gnu.org> wrote:
> > 1350 calls during what time, approximately? less than a second?
> 
> If you've watched the video I've linked

I cannot watch that video, sorry.  But I don't think it matters, see
below.

> you can get a sense of what
> time it takes -- about 15 seconds. Or more if I continue swyping
> rapidly, since Emacs just sits at the bottom eating all input until I
> stop.

I didn't ask how much time it takes Emacs to process the inputs.  I
asked how much time did it take you to generate them by moving your
finger on the touchpad.  I very much doubt the answer to that is 15
sec.

> Touchpad generates about 20-30 inputs per swipe, so I think ~90 inputs
> is maximum human can produce in 1 second

~100 1-line scrolls per second is also a lot, for what Emacs must do
to scroll.

> Can Emacs poll mouse events less frequently?

Emacs doesn't poll the mouse.  The mouse events are received from the
X event queue, together with all the other events: keyboard input,
expose events, etc.  We read the events from X and then process them
one by one.

> > So, once we've established that the touchpad injects 1-line scroll
> > requests at such a high rate, what else needs to be investigated here?
> 
> There I was talking about progressive speed turned on, as it builds up
> almost instantly with my touchpad producing 30 inputs per swipe.

Sorry, I don't understand: what builds up?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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>
> I didn't ask how much time it takes Emacs to process the inputs.  I
> asked how much time did it take you to generate them by moving your
> finger on the touchpad.  I very much doubt the answer to that is 15
> sec.
>

Yes I was talking about me inputting scrolling events for about ~15 secs.
I've rewatched the video and I'm continuously swiping over touchpad for
about ~10 seconds, and Emacs updates position ~5 seconds after I stopped.

> There I was talking about progressive speed turned on, as it builds up
> > almost instantly with my touchpad producing 30 inputs per swipe.
>
> Sorry, I don't understand: what builds up?
>

Scrolling speed. With progressive speed turned on it is impossible to use
touchpad because after single swipe the speed builds up so much resulting
in point immediately jumping to beginning/end of buffer.

>

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Sun, 7 Feb 2021 21:52:22 +0300
> Cc: 46350@debbugs.gnu.org
> 
>  > There I was talking about progressive speed turned on, as it builds up
>  > almost instantly with my touchpad producing 30 inputs per swipe.
> 
>  Sorry, I don't understand: what builds up?
> 
> Scrolling speed. With progressive speed turned on it is impossible to use touchpad because after single
> swipe the speed builds up so much resulting in point immediately jumping to beginning/end of buffer.

With such a rate of input events, isn't that expected?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> Scrolling speed. With progressive speed turned on it is impossible
>> to use touchpad because after single
>> swipe the speed builds up so much resulting in point immediately
>> jumping to beginning/end of buffer.
>
> With such a rate of input events, isn't that expected?

I don't use either a touchpad or a mouse with a scroll button...  but I
seem to remember there being support for coalescing events from a scroll
button in Emacs, at least?  Am I misremembering?

If I'm not, could this also be used in this case, perhaps?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Andrey Orst <andreyorst@gmail.com>,  46350@debbugs.gnu.org
> Date: Sun, 07 Feb 2021 20:37:46 +0100
> 
> I don't use either a touchpad or a mouse with a scroll button...  but I
> seem to remember there being support for coalescing events from a scroll
> button in Emacs, at least?  Am I misremembering?

That's the progressive scroll speed, no?

If not, what did you mean by coalescing here?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> I don't use either a touchpad or a mouse with a scroll button...  but I
>> seem to remember there being support for coalescing events from a scroll
>> button in Emacs, at least?  Am I misremembering?
>
> That's the progressive scroll speed, no?

Oh, yeah.  Sorry.  :-)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Alan Third]

On Sun, Feb 07, 2021 at 09:52:22PM +0300, Andrey Orst wrote:
> >
> > I didn't ask how much time it takes Emacs to process the inputs.  I
> > asked how much time did it take you to generate them by moving your
> > finger on the touchpad.  I very much doubt the answer to that is 15
> > sec.
> >
> 
> Yes I was talking about me inputting scrolling events for about ~15 secs.
> I've rewatched the video and I'm continuously swiping over touchpad for
> about ~10 seconds, and Emacs updates position ~5 seconds after I stopped.
> 
> > There I was talking about progressive speed turned on, as it builds up
> > > almost instantly with my touchpad producing 30 inputs per swipe.
> >
> > Sorry, I don't understand: what builds up?
> >
> 
> Scrolling speed. With progressive speed turned on it is impossible to use
> touchpad because after single swipe the speed builds up so much resulting
> in point immediately jumping to beginning/end of buffer.

This all sounds awfully like the problems we had with the touchpads on
macOS.

On macOS the OS sends inputs with a number of pixels that it expects
the application to scroll, this means it can send hundreds of touchpad
events in a few seconds, but the application is only supposed to
scroll, perhaps, a few tens of lines.

What we do in the NS code is count up the number of pixels and only
send the event to Emacs once it reaches some predetermined "line
size".

I didn't think X worked this way, though, so perhaps it is some
libinput setting.

Or are you using XWayland, which may behave differently than standard
X?
-- 
Alan Third

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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>
> I didn't think X worked this way, though, so perhaps it is some
> libinput setting.
>
> Or are you using XWayland, which may behave differently than standard
> X?
>

I'm using both X (manually selected) and XWayland on two different machines
(both with GNOME Shell). Fedora 32 and 33 respectively if that matters.

>

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Alan Third]

On Mon, Feb 08, 2021 at 01:22:12AM +0300, Andrey Orst wrote:
> >
> > I didn't think X worked this way, though, so perhaps it is some
> > libinput setting.
> >
> > Or are you using XWayland, which may behave differently than standard
> > X?
> >
> 
> I'm using both X (manually selected) and XWayland on two different machines
> (both with GNOME Shell). Fedora 32 and 33 respectively if that matters.

And they all behave the same?
-- 
Alan Third

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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>
> And they all behave the same?
>

Yes. Sorry, should have mentioned that in the first place.

>

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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Also, for some reason scrolling to the buffer's end has much less lag
compared to scrolling to the beginning of the buffer. It's still laggy, but
more manageable

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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And horizontal scrolling is not laggy with touchpad at all. Well, at least
rapid left and right swipes on touchpad aren't creating enormous cpu usage.

So, to summarize:

- scrolling to buffer end  (down) is less laggy than scrolling to buffer
start (up)
- horizontal scrolling isn't laggy at all
- this can be achieved with mouse if you roll it with mouse wheel over the
table very fast

If I can produce more information, maybe stack traces, or more in-depth
profiling please guide me with some instructions. This issue bothered me
for about 2 years, just finally decided to report it.

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bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Mon, 8 Feb 2021 13:12:09 +0300
> 
> Also, for some reason scrolling to the buffer's end has much less lag compared to scrolling to the beginning
> of the buffer. It's still laggy, but more manageable

Scrolling back to the beginning of buffer is more CPU-intensive,
because the functions used for scrolling can only move forward in the
buffer.  So what you see is quite expected.

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Eli Zaretskii]

> From: Andrey Orst <andreyorst@gmail.com>
> Date: Mon, 8 Feb 2021 17:35:51 +0300
> 
> And horizontal scrolling is not laggy with touchpad at all. Well, at least rapid left and right swipes on touchpad
> aren't creating enormous cpu usage.

Horizontal scrolling isn't anywhere as expensive as vertical one.

> - scrolling to buffer end  (down) is less laggy than scrolling to buffer start (up)
> - horizontal scrolling isn't laggy at all
> - this can be achieved with mouse if you roll it with mouse wheel over the table very fast
> 
> If I can produce more information, maybe stack traces, or more in-depth profiling please guide me with some
> instructions. This issue bothered me for about 2 years, just finally decided to report it.

Isn't there some way to control the rate with which the touchpad sends
its events to applications?  Some system-wide setting, perhaps?

bug#46350: 28.0.50; touchpad-scrolling-eats-lots-of-cpu-samples

[Andrey Orst]

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>
> Isn't there some way to control the rate with which the touchpad sends
> its events to applications?  Some system-wide setting, perhaps?
>

As far as I know - no. Wayland didn't standardized this yet, and even for X
there are debates on how to set this properly. Or at least that's what I've
heard. Gnome doesn't have scroll speed settings neither for mouse nor for
touchpad. KDE also lacks this setting AFAIK.

>

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