Compile glxgears from source on Ubuntu 9.10

I decided to modify the source code of glxgears to overcome a peculiar problem. This application would not write the FPS information to file (if redirected) unless it is shutdown.

I checked the source code, glxgears.c and found the problem was simply that there was no fflush statement after the output printf:

static void
event_loop(Display *dpy, Window win)
{

....
if (t - t0 >= 5.0) {

GLfloat seconds = t - t0;
GLfloat fps = frames / seconds;
printf("%d frames in %3.1f seconds = %6.3f FPS\n",frames, seconds,
fps); //no flushing!
t0 = t;
frames = 0;

}}}

}

And so, the solution seemed simple: add the line of code that would force the output buffer to flush (fflush(stdout);) after printf and re-compile the source code.

To be able to compile glxgears.c, however one needs to install many other libraries and packages. Here are the steps that I followed to get the whole thing working.

1. glxgears is part of the Mesa Library. I downloaded th latest source code (MesaLib-7.8.2.tar.gz)


2. Start by untarring this file:

   tar -xvf MesaLib-7.8.2.tar.gz

3. Enter the directory Mesa-7.8.2 and type: ./configure --with-driver=xlib. The configuration code will now start spitting out the libraries that it needs (and which your machine does not have). Following are the libraries that I needed on my machine:


1. libdrm:

   sudo wget http://dri.freedesktop.org/libdrm/libdrm-2.4.21.tar.gz
tar -xvf libdrm-2.4.21.tar.gz
cd libdrm-2.4.21/
./configure
make
make install


2. xorg-macros:

   wget http://mirrors.kernel.org/ubuntu/pool/main/x/xutils-dev/xutils-dev_7.5+4_i386.deb
sudo dpkg -r xutils-dev
sudo dpkg -i xutils-dev_7.5+4_i386.deb
ls /usr/share/pkgconfig/


3. dri2proto:

   wget http://xorg.freedesktop.org/releases/individual/proto/dri2proto-2.3.tar.gz
tar -xvf dri2proto-2.3.tar.gz
cd dri2proto-2.3/
./configure
make
make install


4. glproto:

   wget http://xorg.freedesktop.org/releases/individual/proto/glproto-1.4.12.tar.gz
tar -xvf glproto-1.4.12.tar.gz
cd glproto-1.4.12/
./configure
make


5. xxf86vm:

   sudo apt-get install libxxf86vm-dev

6. xdamage:

   sudo apt-get install libxdamage-dev

4. After all the dependencies are satisfied, ./configure --with-driver=xlib will complete and create the make file.


5. Follow it up with: make. Once you modify the Mesa-7.8.2/progs/xdemos/glxgears.c file, call ./configure --with-driver=xlib and make. The new glxgears executable will be created in the same directory as the souce code.




Writing the output of running glxgears to file

glxgears is a API that people frequently use to test if their graphical user interface works, and though it not a standardized benchmark of how good your GUI is, it does (at least, theoretically) give you some idea of the frames per second that are being rendered on your screen.

When you type the command glxgears in your terminal you should see an animation of rotating gears in the foreground and in the background, the terminal outputs every 5 or so seconds the frames per second that are being used in the rendering...

So now, my problem was simply to get the output of the terminal, that is the FPS values that are getting printed after roughly 5 seconds into a file.

The most obvious solution, that is:

glxgears >> out.txt

does not work. Apparently, glxgears does not flush the values if the output is redirected to file.

I was unable to "solve" the problem (that would require changing the source code of glxgears to make it not only print the output values but also flush it). For now I got something to work which is alright for me. I manually kill the glxgears every 5 seconds, store the output, and then restart another glxgears process.

This is not so trivial actually. If you kill the glxgears using something like

killall glxgears

no FPS values are returned or written to file. Instead you need to shutdown glxgears by telling x-server to withdraw its window resource!

Obtaining GUI access to Xen Domains Using TightVNC

This is a step by step tutorial on how to install a Xen Domain on Xen 3.2 (kernel version 2.6.24-24-xen) and how to get graphical user interface working on it.

I am using a rather ancient version of the Xen kernel because I am short of time at the moment and this is something I have worked with before. But hopefully, I should be able to get the same thing done on a more recent Xen kernel soon.

So to install a new domain from the command line, do:

sudo xen-create-image --hostname=xen_7 --size=1Gb --swap=256Mb --ide --ip=10.5.155.7 --netmask=255.255.240.0 --gateway=10.5.159.255 --force --dir=/home/xen --memory=256Mb --arch=i386 --kernel=/boot/vmlinuz-2.6.24-16-xen --initrd=/boot/initrd.img-2.6.24-16-xen --install-method=debootstrap --dist=hardy --mirror=http://archive.ubuntu.com/ubuntu/


Most of the parameters are self-explanatory. I am using static IP address (10.5.155.7) on my VM. The kernel (vmlinuz-2.6.24-16-xen) and the initial ram disk (initrd.img-2.6.24-16-xen) should be present in your boot directory. Ususally the gateway parameter and the netmask parameter would be the same for your Domain-0 and user domains. To see how much memory is available for the new domain that you are creating use the df or free commands before hand.

Once the new domain has been created you will see a new configuration file in the /etc/xen/ directory. This file needs to be edited a little bit as follows:

# Configuration file for the Xen instance xen_7, created
# by xen-tools 3.8 on Thu Sep 2 19:12:55 2010.
#

#
# Kernel + memory size
#
kernel = '/boot/vmlinuz-2.6.24-16-xen'
ramdisk = '/boot/initrd.img-2.6.24-16-xen'
memory = '256'
vcpu = '2'

#
# Disk device(s).
#
root = '/dev/hda2 ro'
disk = [

'tap:aio:/home/xen/domains/xen_7/swap.img,hda1,w',
'tap:aio:/home/xen/domains/xen_7/disk.img,hda2,w',

The text in red shows the text that has been changed/added. The vcpu parameter can be used if your want your domain to have more than one virtual processor. Later when your machine has booted you can check that this is indeed the case from the /proc/cpuinfo file.

So now we are all set to boot up our machine. In the Domain-0 terminal, type:

sudo xm create /etc/xen/xen_7.cfg


You could monitor the booting up and working of your new domain from Domain-0 using xentop and

sudo xm list


To access your machine, use:

sudo xm console xen_7


Login as root and set your new password using passwd command. If the network on your new domain is not functioning for some reason, look at this post for possible ways to correct the problem.

So at this point you have a functioning domain that you can access via the terminal. But now we want to get GUI access using tightVNC. To do this, a truck load of software needs to be installed. I have used the dpkg --get-selections option to generate a list of all the software that I needed on my machine. Use the dpkg --set-selection command followed by dselect (Select the "install" option on the interface opened by dselect) to install all the packages in the list.

Now the client/remote machine from which you want to access the graphical user interface of your domains needs to have VNCviewer ( sudo apt-get install vncviewer) installed.

On the host (guest domain) terminal, do:

Xvfb :0 -screen 0 800x600x16 &
export DISPLAY=:0
x11vnc -display :0&
xterm&


You can check that the Xvfb and xterm processes have started from the list of running processes. (ps uax)

On the client machine, do vncviewer 10.5.155.6:0 . You should see the GUI interface at this point. To test that the graphics are working, try:

glxgears

Well, that's it! You should see an animation of a bunch of gears rotating on your screen.... Which means that you have a GUI access to your machine!