I am experiencing some serious performance issues with my Ubuntu 12.04 setup and thus looking for the culprit by running htop alongside my usual tasks.

Aside from the usual suspects like chromium, compiz and conky, I noticed this process:

/usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch -background none

Not only is it running constantly, but it's also one of the main ressource hogs in the process list, both in regards of cpu usage as well as memory consumption. It's the number one performance eater most of the time, only topped from time to time by an especially ressource-hungry task like flash player or the like.

Judging by the name, I'm totally unsure what it does. X and lightdm seem to indicate a relation to the gui while tcp seems network related.

My question(s): is this process supposed to run all the time? Is it legit that it uses this much ressources? Do I need it to run or is it safe to kill, if so, how to?

FYI: My system is completely up-to-date, I'm even using the xorg-edgers ppa for the very latest nvidia drivers and compiz-packages (for specific bug-related reasons).

Any suggestions would be very much appreciated.

  • 2
    If you kill it, you'll lose your GUI until you either reboot your computer or know how to restart the X server. – Braden Best Apr 13 '13 at 22:10

This is the system graphics server and should not be killed. It converts the layout of desktop applications into low-level drawing operations on your graphics card, and routes keyboard and mouse input to the correct application that should receive them.

The reference to LightDM is that this is the first client it starts (the Ubuntu login screen); the reference to tcp is because X is designed to be network-transparent - it can work quite happily with input devices, applications and display devices all running on different computers. (I think that in Ubuntu it is configured not to accept network connections, only those coming through SSH, but may be wrong).

Check the statistics you are using are for X itself rather than X and children, since the children include all applications you run in a graphical environment. Excess resource usage by X itself is usually down to misbehaving desktop applications, but this can be very hard to debug.

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That's the X server. That's the graphical interface of which all other graphical applications are clients to.

  • Yes it's supposed to run all the time.
  • LightDM is just the login manager that loads first
  • Using a lot of resources is usually a sign that X is either struggling with a crappy driver or that there's a crappy application (historically usually Compiz) trying to push a driver too hard.
  • Using xorg-edgers is a good way to run crappy untested software. Read the PPA description and decided if you want to use ppa-purge. The newest nvidia drivers can be installed without upgrading X.
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  • Thanks for your answer. As I pointed out, my use of xorg-edgers is strictly bug-related. I know about the risks but they are nothing compared with the issues I had to suffer otherwise. I hope to get rid of it again soon, but that depends on what bugfixes are backported from quantal. Thanks for the warning, though. – FuzzyQ Aug 24 '12 at 10:20
  • That's why I'd suggest not using the PPA it and manually installing the driver from Nvidia. Run the stock (tested) versions of X and still get your initial bug fixes. Then you'll find out if the problem isn't actually just another bug in the Nvidia driver — which could then be reported to Nvidia so that it gets fixed... – Oli Aug 24 '12 at 10:25
  • There are several bugs I suffer from. Some are kernel-related, others are nvidia-driver related, most are compiz-related. I tried to install the latest versions of these three one-by-one but failed. I wasn't able to install any nvidia-driver (from repository or manually) after the kernel update. Only after installing some libraries from xorg-edgers was I able to get the driver running. Plus, this ppa brought more stability than any of my own attempts to solve the problems. To be honest, I never noticed any issues in the past from using this ppa I hadn't otherwise, too. – FuzzyQ Aug 24 '12 at 10:43

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