XOpenDisplay takes a long time to return

[Divick Kishore]

Hi,
    I have installed nvidia OpenGL drivers on amazon gpu cluster
instance which has two Tesla M2050 GPUs and I see a weird behavior
when I run any two apps in quick succession.

I am running the server in a headless mode with xorg.conf generated
using the following options:

sudo nvidia-xconfig -a --no-xinerama --no-dynamic-twinview
--use-display-device=None --virtual=1280x1024

which maps two screens each of them to two devices.

Finally I run X Server using:

sudo /usr/bin/X :0

and then I run any application on any one of the GPUs using:

#Runs it on first GPU
export DISPLAY=:0.0 glxgears

#Runs it on second GPU
export DISPLAY=:0.1 glxgears

I noticed that sometimes it takes a very very long time (~couple of
seconds to a minute) before a call to XOpenDisplay succeeds. It is not
clear if the issue is with X server or with nvidia drivers or possibly
with my xorg settings.

I notice that when an application exits the output is similar to the
following output (see below below this paragraph) on the terminal
where I started the X. Only when this is dumped when the previous
application exits / closes the display, the XOpenDisplay succeeds. So
it seems that only after either the driver of X does some cleanup the
subsequent XOpenDisplay succeeds.

12 XSELINUXs still allocated at reset
SCREEN: 0 objects of 344 bytes = 0 total bytes 0 private allocs
COLORMAP: 0 objects of 8 bytes = 0 total bytes 0 private allocs
DEVICE: 0 objects of 104 bytes = 0 total bytes 0 private allocs
CLIENT: 0 objects of 152 bytes = 0 total bytes 0 private allocs
WINDOW: 0 objects of 72 bytes = 0 total bytes 0 private allocs
PIXMAP: 4 objects of 112 bytes = 448 total bytes 0 private allocs
...
...
TOTAL: 8 objects, 320 bytes, 0 allocs


Is there someone who could help?
Regards,
Divick