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.




Altering the behavior of CTRL-C

Short piece of code that might come in handy. One can use the "trap" procedure to alter the behavior of Ctrl-C which is often used to interrupt execution. One can use the altered behavior to delete back-ground processes or remove temporary files that might otherwise keep lying around.. So here is the src code which you can add anywhere in your script.

# trap ctrl-c and call ctrl_c()
trap 'ctrl_c' 2

function ctrl_c() {

pkill temp_processes
#run clean up code here ...

}

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!

Issuing commands to VLC and collecting output to file

So, I wanted to play a video using VLC Media Player and collect statistics like lost frames and bit rate into a file every x seconds while the video is running. Seems pretty straight forward considering that the stats can be viewed from the VLC GUI. So it should be a straight forward matter to get them into a file, right? Wrong !!

I tried several approaches including using the rc interface. Pierre gave me a piece of code that solves the problem on his machine:

while true; do echo stats; sleep 2; done | vlc -I rc filename > out.txt

Here, the filename is the name of the file that needs to be played and the number following sleep is the time between two reads of the statistics. As you can see, all this piece of code does is to issue (using pipe |) stats command to the rc interface (denoted by the -I option) every 2 seconds and store the output into out.txt file. For some reason the same code did not work on my machine and I kept getting the error message:

user@machine:~$ while true; do echo stats; sleep 2; done | vlc -I rc 350animation2.mpg > out.txt

VLC media player 1.0.2 Goldeneye

[0x8731750] main interface error: no suitable interface module

[0x8685140] main libvlc error: interface "default" initialization failed

I am using VLC media player 1.0.2 and my OS is Ubuntu Karmic Koala.If anyone has a clue as to what could be causing the problem, please send me a comment. Between, I was able to redirect the output stats to a file using the rc interface. For that I started VLC using vlc --intf rc filename >output.txt and then in the interface that opens, I issued the stats command. What I could not do was to automate the process of issuing the stats command every x seconds.

While trying to resolve the issue, I stumbled upon this "Not a blog" where the author shows how to issue commands to VLC from the command line using netcat and UNIX sockets. I tried to extrapolate from the code and tweak it to channel the collection of stats but it did not work. My super naive attempts basically were along the lines of writing a bash script that starts the video and then runs in an infinite loop trying to collect stats and sleep, as shown below:

echo play 350animation2.mpg
while true
do

echo stats
sleep 2

done

Then I would redirect the input and output to the VLC interface. But the same error message persisted. David Wolinsky came to the rescue. Here is the script that he come up with:

#!/bin/bash

set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1)
set -o nounset

set -m

run() {
pid=$1
sleep 4
while true; do

echo -n "stats" | nc -U vlc.sock
if [[ ! $(ps uax | grep -v grep | grep $pid) ]]; then
return
fi
sleep 2

done
}

vlc -I rc --rc-unix vlc.sock 350animation2.mpg &> out &
pid=$!
run $pid &
fg %1

As you can see, this code uses the UNIX socket approach as well. After the VLC process is started, the PID is stored and used to start the run script on the top. The output gets stored in the out file. The fg (fore ground) command in the end is apparently necessary.

Thanks to Pierre, David and Andrabr for help with this problem!

How to get Virtual Manager to work for a Xen host

So, continuing with the theme of Xen, Virtual Machine Manager or virt-manager for short, is a piece of software that I decided to check out because I wanted graphical access to my virtual machines. A more formal description as given on their website is:

"Virt-manager is a desktop user interface for managing virtual machines. It presents a summary view of running domains, their live performance & resource utilization statistics. The detailed view graphs performance & utilization over time. Wizards enable the creation of new domains, and configuration & adjustment of a domain's resource allocation & virtual hardware. An embedded VNC client viewer presents a full graphical console to the guest domain"

You need to download virt-manager on the machine from which you wish to access your virtual machines. I am using a machine running Ubuntu 10.04 which I will call the client machine in the description below.

My Virtual Machines (VMs) were created on top of Xen 3.2 hypervisor, Earlier I had some issues getting the network up and running on my VMs, the resolution of which I have described in an earlier post. My hypervisor machine which I will call my host machine is running kernel 2.6.24-24-xen.

So here is the procedure that I followed to get virt-manager to work:

1. I used the Synaptic Package Manager (System->Administration->Synaptic Package Manager to download virt-manager and all the dependencies on my client machine. Alternatively, one could also do sudo apt-get install virt-manager


2. On my host machine, I downloaded and installed libvirt-bin and ssh-askpass

   sudo apt-get install libvirt-bin

   sudo apt-get install ssh-askpass



3. Now to access the virt-manager console from my client machine I used Application->System Tools->Virtual Machine Manager


4. On my host machine, I started the libvirtd daemon:

   sudo libvirtd start



5. At this point I tried to connect to my host machine using File->Add Connection...; I chose my specific hypervisor (Xen) and Connection as Remote Tunnel over SSH (I am not sure that this is the one that I was supposed to use, but it did work, eventually!)
   
   At this point, I got the following error on a pop-up on my client machine and on the console of my host machine:

   libvir: Xen Daemon error :internal error failed to connect to xend

   After some effort, the following fix worked:

   
   
   1. Open the xend configuration file

      sudo vim /etc/xen/xend-config.sxp

   
   
   2. In my previous post I had talked about adding a temporary bridge between physical network device and the virtual TAP device. I had to let the xend daemon become aware of this. So under the line:

      (network-script network-bridge)

      I added:

      (network-script 'network-bridge netdev=tmpbridge')

      (To recall what my network device is called, I did a ifconfig. It was the one whose description contains the domain-0's IP.
   
   
   3. I was not done with this file yet. I needed to add the following line somewhere in the file:

      (xend-unix-server yes)

   
   
   4. I saved and closed the file. Restarted the host machine's network (sudo /etc/init.d/networking restart), restarted the xend daemon (sudo xend restart), and finally restarted the libvirtd daemon( sudo libvirtd start)
      

   
   Now when I tried to add the connection using the setting mentioned above, it went through, asked me for a password and I would see a table giving the details of the CPU utilization and some other statistics of my VMs. Following is a screen shot of what I can see so far:
   
   
   

No network on Xen user domain

Today I installed Xen 3.2 for my work and created a guest VM using the this link as a guide. However I found that the network on my VM didn't work. The problem as Pierre explained was that the link between my physical network device and the virtual TAP device was not set up.

This was in spite of the fact that I re-started the xend daemon on my machine and used the static IP address method that was recommended in the blog mentioned above.So it seems that the xm create and xend scripts are not doing what they are supposed to do!

David Wolinsky came up with the following fix:
On the console of your control domain, do the following:

$ brctl addif tmpbridge eth0
$ ifup tmpbridge
$ ifconfig eth0 0.0.0.0 promisc
$ brctl show
$ dhclient tmpbridge

Now when you do an ifconfig on you domain-0, the tmpbridge interface should show up with the IP that was originally assigned to eth0.

And since eth0 is set to "promiscuous" mode, it will accept all network packages coming to it.

Now using the route command find the default gateway used by your domain-0. The following terminal snapshot is provided to clarify which IP I am talking about:


user@Domain0:~$ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.5.144.0 * 255.255.240.0 U 0 0 0 tmpbridge
default 10.5.144.1 0.0.0.0 UG 0 0 0 tmpbridge



In the last line, the default gateway is highlighted in red. Make a note of this IP.
Now open the console of your user domain and check the route:


root@UserDomain:~# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.5.144.0 * 255.255.240.0 U 0 0 0 eth0


As you can see, in my case the default gateway was not set. To do so use the route add default gw command and the IP we obtained from the default gateway of domain-0.


root@UserDomain:~# route add default gw 10.5.144.1


Verify using route, and then try pinning something:


root@UserDomain:~# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.5.144.0 * 255.255.240.0 U 0 0 0 eth0
default 10.5.144.1 0.0.0.0 UG 0 0 0 eth0
root@UserDomain:~# ping google.com
PING google.com (72.14.253.104) 56(84) bytes of data.
64 bytes from mia04s03-in-f104.1e100.net (72.14.253.104): icmp_seq=1 ttl=56 time=15.5 ms
64 bytes from mia04s03-in-f104.1e100.net (72.14.253.104): icmp_seq=2 ttl=56 time=14.0 ms
64 bytes from mia04s03-in-f104.1e100.net (72.14.253.104): icmp_seq=3 ttl=56 time=13.9 ms



Dadaaa! Many thanks to Pierre and David!
As a side note, if you are adding more domains, you do not need to repeat all the commands on domain-0, as its interface is already in the "promiscuous" mode. Only run the dhclient again. You will however need to set up the default gateway in every new domain that you create.