Hello,

When I decided to upgrade to the new version of Emacs - 25.1 I started
getting very slow text scrolling. With all my packages loaded and in
Python mode emacs is completelty unusable because there is a about half
a second delay after every down arrow press.

Moreover, I then tried emacs -Q and opened my init.el. Pressed on the
down arrow key and holding it caused sluggish scrolling when the cursor
reaches somewhere around the half of the init.el.

I have also run the profiler while in emacs -Q and init.el:

- command-execute                                                2337  96%
 - call-interactively                                            2337  96%
  - funcall-interactively                                        2311  95%
   - next-line                                                   1991  82%
    - line-move                                                  1991  82%
     - line-move-partial                                         1356  56%
      - window-screen-lines                                         2   0%
       - default-line-height                                        2   0%
          default-font-height                                       1   0%
       line-move-visual                                           423  17%
   - previous-line                                                320  13%
    - line-move                                                   320  13%
       line-move-visual                                           161   6%
  - byte-code                                                      26   1%
   - read-extended-command                                         26   1%
    - completing-read                                              26   1%
     - completing-read-default                                     26   1%
        read-from-minibuffer                                       26   1%
+ ...

For now I reverted using emacs 24.5 and with it I don't have such
problems.
It's quite strange because at home I'm using Ubuntu and emacs 25.1
doesn't have problems with scrolling. It's only happening on my computer
at work running Windows 10.

Just in case, I'm writing this mail from emacs -Q so you can see my
context:

In GNU Emacs 25.1.1 (i686-w64-mingw32)
 of 2016-11-16 built on LAPHROAIG
Windowing system distributor 'Microsoft Corp.', version 10.0.14393
Configured using:
 'configure --host=i686-w64-mingw32 --without-dbus
 --without-compress-install 'CFLAGS=-static -O2 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: BGR
  locale-coding-system: cp1251

Major mode: Emacs-Lisp

Minor modes in effect:
  diff-auto-refine-mode: t
  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

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode cl-loaddefs pcase
cl-lib mail-prsvr mail-utils vc-git diff-mode easymenu easy-mmode
time-date mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel dos-w32 ls-lisp disp-table w32-win w32-vars
term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame 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 charscript case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
w32notify w32 multi-tty make-network-process emacs)

Memory information:
((conses 8 93915 10745)
 (symbols 32 20061 0)
 (miscs 32 95 181)
 (strings 16 17370 3420)
 (string-bytes 1 476444)
 (vectors 8 12905)
 (vector-slots 4 445216 3224)
 (floats 8 165 30)
 (intervals 28 433 42)
 (buffers 520 21))


-- 
//