[arch-general] Keyboard lag issue

[Manuel Groß]

On Mon, 20 Jun 2016 22:55:35 +0200
Gaëtan Harter via arch-general <arch-general at archlinux.org> wrote:

> On Mon, Jun 20, 2016 at 7:17 PM, Manuel Groß <mgr at nordkrater.de>
> wrote:
> 
> > Hello there,
> >
> > I currently experience a weird keyboard lag issue which I yet failed
> > to resolve. I had some help looking into it a bit (and obviously
> > searched the web), but we couldn't identify the speficic problem. I
> > hope someone could provide me pointers or hints on what to test out.
> >
> > I have a Thinkpad x250 running Arch Linux with Openbox and X11 on
> > it. I use systemd-logind to log in, so X is started with the 'exec
> > openbox-session' from my xinitrc. Not from some fancy lightdm or so.
> > I do not have a certain date since when the issue occurs, but it has
> > probably been a little over a month. I didn't make any major
> > changes to my system then, and I do update regularly. This didn't
> > occur when I set up the system.
> >
> > The issue is, that on some, certain programs, the keyboard input
> > 'arrives' too late, with delays up to 1-2s. In other programs, this
> > never happens at all. And in rare occasions, it is even fine for
> > programs, in which I experience the problem.
> > I checked logs at obvious locations, but neither the systemd
> > journal, dmesg or the Xorg log were screaming 'I have an issue
> > here'. The trackpoint always works as excpected and the touchpad is
> > disabled.
> >
> > Programs where the delay occurs:
> >  * sakura
> >  * sublime
> >  * wireshark (qt5 version)
> >
> > Programs which are fine:
> >  * claws-mail
> >  * geany
> >  * xterm
> >  * chromium
> >
> > The delay also never occurs in the system shell (Alt+F2) and xterm,
> > so it's not the shell or oh-my-zsh.
> > The program lists suggests, that it is not a problem due to a
> > specific version of GTK or QT, since programs using either library
> > (or none of them) are affected.
> >
> > I tried using 'libinput' instead of 'evdev' as a keyboard driver,
> > but the change had no effect (I double checked the Xorg log which
> > driver was actually used).
> > In 'xev', all keystrokes arrive immediately.
> >
> > So seems not to be the kernel or the driver, nor a specific gtk or
> > qt library.
> > The next thing to test would probably be the xlib and the libxcb
> > themselves. So I used 'downgrader' to downgrade each a few revisions
> > (also their lib32-libraries) and checked for a change, without
> > success.
> >
> > I don't know what to try next. Does anyone of you have an idea or
> > already solved a similar issue? I'd appreciate any help on this.

> Hi Manuel,
> 
> I have a Thinkpad T440p and I have the same issue with kernel 4.6,
> with both 4.6.2-1 and 4.6.1-XX versions.
> There is no issue with lts kernel 4.4.13-1.
> 
> From what I experienced, gnome-terminal is impacted, and I think also
> firefox.

Hello Gaëtan, thanks for your response!

I just downgraded the kernel to 4.5.4-1, which I had installed before
the 4.6 versions and was still available in my pacman cache. This seems
to resolve the issue for me, too.

Did you report a bug? 
I don't think I feel comfortable with bisecting the kernel on my
productive system right now, but I'd still like to update my kernel in
the future ;)
-- 
Grüße/Regards
Manuel Groß
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <https://lists.archlinux.org/pipermail/arch-general/attachments/20160620/346db2c6/attachment.asc>