Mouse lag and ksmserver

[Patrick O'Callaghan]

On Fri, 2015-10-16 at 00:40 +0100, Patrick O'Callaghan wrote:
> It's hard to know whether these two things are connected, but I'll
> mention them together since they seem to have been correlated at
> least
> once:
> 
> I often find that after being logged into Plasma session for a few
> days, the cursor starts to lag noticeably behind my wireless
> (Bluetooth) mouse movement, to the extent that the mouse becomes
> quite
> difficult to use. It's hard to determine just what causes this. At
> one
> point I suspected either Chrome or Firefox, perhaps because some Web
> page was very loaded with Javascript, but last time I killed both of
> them and it seemed to make no difference.
> 
> I have a second mouse (MS wireless connected via a USB dongle) and
> its
> behaviour is always entirely normal, i.e. no lag. I've tried using
> Gnome but haven't managed to reproduce this behaviour, though I also
> haven't tried very hard.
> 
> When this problem cropped up just now, after several days of not
> appearing, I checked "top" and found ksmserver taking 13% of CPU, far
> above anything else. This is an 8-core Intel i7 with 16GB of RAM (and
> root on an SSD).
> 
> I logged out of the session and logged into a console. ksmserver CPU
> usage went up to 100% and stayed there. I rebooted and everything
> went
> back to normal, i.e. no mouse lag and ksmserver taking no appreciable
> CPU time.

And now I'm getting the lag again, but without the ksmserver problem,
so they are probably unrelated.

poc