odd pauses using GUI

[Karl Auer]

When using my laptop, the GUI stops responding for many seconds at a
time. 

The only clue I have, really, is that there was some kind of driver
conflict for my NVidia graphics that was preventing X starting up. I had
to uninstall nvidia* and reinstall them. In so doing I did NOT reinstall
nvidia 304, because that was what was conflicting. Now things look like
this:

   kauer at karl:/var/log$ dpkg --get-selections | grep nvidia
   nvidia-173					install
   nvidia-common				install
   nvidia-settings				install

Now (and I am not saying this relates to the above conflict) my system
is pausing all the time, for anything up to a minute. During these
pauses the mouse cursor still moves around, but it doesn't change as it
moves over window edges or title bars. Some clicks seem to register
during this time, and are processed when the system unpauses, but not
all. Keypresses are registered and "play back" when the system unpauses.
During a pause, no part of the screen image updates except for the mouse
moving. Sometimes it will pause mid-move, with a window half-opaque, but
that's just happenstance. The window movement completes when the system
unpauses.

I have tried other GUIs - Ubuntu, Ubuntu2D, Gnome, Gnome Classic and
Gnome Classic with no effects. All show the exact same symptoms.

During a pause, the hard disk is inactive. SMART status on the drive is
good - a few bad blocks, but OK (SMART status shows green in the disk
utility).

top shows no processes exceeding normal CPU usage, and the little
task-bar CPU meter shows no undue load. The CPUs are not heating up and
the fan is not running more than usual.

There is no correlation between the pauses and network activity as far
as I can tell.

It does seem to be related to screen changes. Working inside some
applications (notably LibreOffice3), the pauses don't seem to happen,
but moving the mouse cursor outside the window - so that the focus
changes or whatever - will often trigger a pause. Inside some
applications, almost everything seems to trigger pauses - editing an
email in Evolution, for example is very tedious.

There is no change if I disconnect the USB mouse and use the touchpad,
but as the mouse is about the only thing that doesn't seem affected by
the pauses, I'd say the USB subsystem is not the issue.

This is on a laptop running Gnome3 in Ubuntu 12.04.4. I'd like to
replace the video subsystem to get everything back to the right versions
etc, but I don't know how :-( As mentioned, I've already uninstalled
nvidia* and put it back.

Time to reinstall? Other ideas gratefully received.

Regards, K.


-- 
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Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://twitter.com/kauer389

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