Created attachment 1237311 [details]
Description of problem:
Since the update to F25 output lag in xterm has become much more noticeable.
There is sometime significant delay in updating the screen (for example pressing enter on a full screen shows the last line duplicated before the lowest line is cleared)
Showing fast scrolling content also is significantly slow, and often only shows content in the upper half of the window, while the lower half stays in background color.
Version-Release number of selected component (if applicable):
Show the first 20000 lines from /usr/share/dict/words and time the output using
time head -n 20000 /usr/share/dict/words
xterm with the configuration as attached:
xterm started as "xterm -fa 'Inconsolata Medium 10'":
(also the scrolling feels a lot smoother, and less blank space is seen at the bottom of the screen)
gnome-terminal using 'Inconsolata Medium 10' as the font:
(no noticeable delay)
Desktop environment is Cinnamon.
urxvt started as "urxvt -fn 'xft:Fixed:pixelsize=14:weight=80'":
(this looks, to my eyes, exactly as xterm in the default configuration in terms of font rendering)
It would be interesting to see a perf (or oprofile) report. I suspect it might be a problem in the X driver or the font rendering.
I've attached the output directory created by a run of
operf xterm -e 'bash -c "head -n 20000 /usr/share/dict/words"'
Created attachment 1238252 [details]
Thanks for the data. I don't see anything suspicious there. I'd still suspect something with X or the X driver. Can you try downgrading xterm to the fc24 package and see if it changes anything?
If you are ok with "missing" some data when scrolling, you can enable the fastScroll X resource for xterm. That should give similar performance as the other terminals.
There seems to be something to this. Taking a system wide profile during the event shows a lot of time being spent in the intel xorg driver (and a lot of CPU time in WAIT).
I still have the raw oprofile data for this, but as far as I can see to make sense of it this requires debuginfo for the exact binaries.
I've attached the new oprofile data dump, the list of installed debuginfo packages and the output I get from opreport.
Created attachment 1239590 [details]
oprofile system wide output
Created attachment 1239591 [details]
Created attachment 1239592 [details]
Created attachment 1239597 [details]
Xorg log file
Ok, let's see if the maintainers of the X driver have any ideas.
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