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[Bug 1616981] [NEW] Using OpenGL with a Displaylink-Adapter leads to high CPU usage


Public bug reported:


First of all: thank you so much for your work! I have been using
Unity/Compiz for a couple of years now and have been very happy with
this software. Thank you for making this possible for so many people.
God bless you for that!

I have since a couple of weeks a multi-monitor configuration like this:
 - Monitor A: laptop internal monitor
 - Monitor B: external monitor connected directly to the laptop
 - Monitor C: external monitor connected to a USB-DVI adapter which is connected to the laptop

The hardware is:
 - Intel HD3000 in the laptop
 - HP NL571AA USB-to-DVI adapter using a Displaylink chip

My problem is this:
 - Show video on C --> CPU usage of Displaylink driver is high
 - Show video on monitor A or B --> CPU usage of Displaylink driver is equally high

Expected behaviour: 
 - CPU usage of Displaylink driver is not high when monitor C is connected and is showing only static content 

If I disable the compiz OpenGL plugin using ccsm the CPU load of the
Displaylink driver is almost zero if I don't use monitor C, as expected.
The problem is of course I then can't drag windows anymore so the
desktop is becomes unusable.

According to this post
http://displaylink.org/forum/showpost.php?p=79485&postcount=6 this issue
is known by Displaylink and has to be solved somewhere else.

My question is: could/should this be solved in compiz? If so, I would be
willing to help with the programming if I can.

** Affects: compiz (Ubuntu)
     Importance: Undecided
         Status: New

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  Using OpenGL with a Displaylink-Adapter leads to high CPU usage

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