Chris Tyler's Blog - X Window System (X11)

GNOME 3 Lunchtime Talk

nospam@example.com (Chris Tyler) — Sat, 19 Mar 2011 00:58:18 -0400

The participants in the GNOME documentation hackfest led a great lunchtime talk on Friday, introducing GNOME 3 to about two dozen Senecans.

GNOME 3 embodies a complete re-design of the desktop. Clutter has been replaced with discoverable behaviours, visual cues, and generally streamlined operation. It's a bold experiment that has already attracted some detractors, but it was fascinating and enlightening to hear the environment explained by members of the community that created it. I'm looking forward to using GNOME 3 in the upcoming release of Fedora 15.

There were many who expressed an interest in attending but were unable to do so. Here are a couple of links:

GNOME 3 site, with features, screenshots, and FAQ: http://www.gnome3.org/
Main GNOME site: http://www.gnome.org/

Many thanks to the GNOME documentation team for the talk.

Dear Lazyweb: How can you find a process ID given a window ID?

nospam@example.com (Chris Tyler) — Mon, 23 Nov 2009 15:14:34 -0500

As far as I know, there is no way to reliably get a process ID from an X window ID for local clients (to implement Richard's View Source idea). I would love to be wrong!

Questions:

(1) Did I miss something? Can this be done now?

(2) If this can't be done now, what would it take? Could we create an X extension so that the server can supply connection info for a window, and then trace that connection info back to a specific process?

Multiseat

nospam@example.com (Chris Tyler) — Wed, 25 Mar 2009 09:01:46 -0400

I haven't written about multiseat for a while.

Bad news first: you can't do (multi-card) multiseat on F10 using open-source drivers, and you won't be able to do it in F11 either. David Airlie's work on the Radeon driver is getting close, but there's still a crash-on-exit last time I checked.

Slightly good news: you can sometimes do multi-card multiseat on Nvidia hardware using the proprietary driver on F10/F11, if the phase of the moon is right. I have it working on a dual-PCIe system, but on another dual-PCIe+dual-PCI system (4 seats), I can only get three of the seats active at once.

Better news: I'm hopeful for the F12 timeframe.

More to follow...

Multiseat on Dual ATI and Dual NVIDIA

nospam@example.com (Chris Tyler) — Sat, 07 Feb 2009 15:15:00 -0500

I haven't had a clear picture of where the current X drivers stand in terms of multiseat and multicard support. So, after a week of fighting with drivers, video cards, feisty GPU power cables and hard disk drives mounted in such a way that they block PCIe slots, I've compiled this table of the state of current ATI and NVIDIA drivers (excuse the width of the table):

Hardware	Driver	Result	Notes
Dual ATI R710 (Asus EAH4550)	radeon (xorg-x11-drv-ati-6.10.0-1.fc10.x86_64)	System locks up on X server exit, otherwise works with multiseat configuration	freedesktop.org bug 19956
Dual ATI R710 (Asus EAH4550)	radeonhd (xorg-x11-drv-radeonhd.x86_64 1.2.4-1.1.20081212git.fc10)	Multiseat configuration starts, but requires setpci command, has has image corruption on 2nd display at resolutions above 1280x1024, and becomes progressively slower on 1st display over time. Text VT is unusable after X server terminates	(List server for radeonhd list not functioning?)
Dual NVIDIA 9800GTX (Asus EN9800GTX+)	vesa (xorg-x11-drv-vesa-2.0.0-1.fc10.x86_64)	Kernel oops	Didn't expect to work
	nv (xorg-x11-drv-nv-2.1.12-6.fc10.x86_64)	System lockup	Known not to work by upstream
	nouveau (xorg-x11-drv-nouveau-0.0.11- 1.20081119git65b956f.fc10.x86_64)	Kernel oops	Known not to work by upstream
	nvidia (xorg-x11-drv-nvidia-180.25-1.fc10.x86_64 from rpmfusion via kmod-nvidia)	Works without error	Proprietary driver

Testing was performed using Fedora 10 and Xorg 1.5.3 on an Asus P5E3 Premium motherboard with an Intel Q6600 processor, using BusID sections in X server configuration files to start a separate X server for each seat, turning off AutoAddDevices, using the evdev driver with device lines for each manually-configured keyboard/mouse input device (/dev/input/eventX), and starting the X servers with --sharevts. Initial tests did not use a display manager; later tests on drivers that passed the first tests used xdm (with mixed success).

At this time, the radeon driver appears to be the Open Source driver closest to being able to run a multiseat, multi-card system. I tried to find out more about the cause of the radeon lockup, but single-stepping with gdb yielded the only successful exit from the X server (!!!), and in every other case the system lockup has prevented me from getting useful information.

Some notes:

xdm causes SELinux AVC denials in this configuration as packaged in F10 (writing a temp file), and displays a message on the login dialog about the displays being insecure (?).
Current console policy assumes a single seat. This has an impact on sound use; it probably also affects removable storage, but I did not test this.
The radeon driver runs glxgears at about 100-200 fps on each of two seats. The nvidia driver runs glxgears at about 600 fps on each of the seats. Oddly, glxgear startup under the nvidia driver complains about /dev/nvidiactl being unwritable, but it runs; however, making /dev/nvidiactl writable prevents glxgears from starting successfully.

Next round: layered (Xephyr-on-X) servers for multiseat on a single card.

Multiseat on Dual ATI R710's - Working

nospam@example.com (Chris Tyler) — Mon, 02 Feb 2009 17:29:39 -0500

I finally got a 2-seat system working reliably on dual ATI R710's (Asus EAH 4550s) this afternoon, using F10. The stability problems I mentioned earlier cleared up when I reduced the set of services running -- the important stuff (dbus, NM, hal) are all still enabled so I need to do some more checking to find the conflict (isdn? bluetooth?).

More tests to follow, but it's encouraging to know that there is at least one Open Source driver that can be used to build a multiseat system with the current X server. I'll blog details in the next day or two.

Multiseat - radeonhd

nospam@example.com (Chris Tyler) — Mon, 02 Feb 2009 15:03:59 -0500

Two users, two monitors, two mice, two keyboards, two ATI video cards, one computer. Now if it would just stay stable while the mice and keyboards are being used, like in the good old (F8) days...

Multiseat on Dual ATI R710's - So close!

nospam@example.com (Chris Tyler) — Mon, 02 Feb 2009 13:08:24 -0500

I've been trying to see if there's any hope of running multiseat with the current X.org server and open source drivers. I think the two most likely hardware scenarios are 2+ recent ATI cards or 2+ recent NVidia cards, so I'm focusing on testing those configurations on some new hardware at Seneca, using F10 so far (Rawhide soon).

So far I've been working with two ASUS EAH4550's (PCI-Ex16 ATI R710) on a system with an Asus P5E5 Premuim motherboard. After much experimentation, it looks like:

- The kernel option "pci=rom" is not required (contrary to the radeonhd web page).

- The xorg.conf accepts the BusID option in the "Devices" section to specify each card, the evdev "AutoAddDevices" option turned off in ServerFlags, and InputDevice sections specifying the evdev driver and the /dev/input/eventX devices for keyboard and pointer.

- These setpci commands are required to make the card's AtomBIOS visible to the radeonhd driver (on this hardware):

setpci -s 0000:01:00.0 COMMAND=2

setpci -s 0000:02:00.0 COMMAND=2

(Setting "UseAtomBIOS" off does not work -- without these lines, the X server will not start up).

- The cards may be started one-at-a-time, and work reliably with the designated keyboard and mouse

- Two X servers may be started at the same time, one for each seat. The VT switch that takes place when the second one starts will make the first screen blank out. Terminating the second X server causes the first one to reappear. These sessions seem robust/reliable (I can start gnome-session for two separate users, and do productive work on them).

- Adding the "-sharevts" option to the X server command line causes both seats to be active at the same time (the -novtswitch option is not needed). The servers will apparently run forever without user input, but shortly after I start using any of the keyboard/mice, the system locks up pretty tight (no network access, displays frozen). Sometimes I can enter enough keystrokes to start an app or two, and they also run fine as long as there are no input events.

So this feels pretty close, but short of setting up a serial console I don't know how to find out what's causing the two-seat lockups.

Next up: checking out Nvidia (I'm not hopeful, at least with the open source drivers).

Multiseat for F11!

nospam@example.com (Chris Tyler) — Mon, 10 Nov 2008 10:13:09 -0500

I use a multiseat system at home: one PC, four monitors, four mice, four keyboards, and four soundcards, used by four people simultaneously. It works well, and I like it because it requires less hardware, electricity, and administration effort than four networked PCs. That system is running Fedora 8, for which support will end on Christmas day.

Why not update to Fedora 9 or 10? Because I can't. The (wonderful) changes in X, GDM, and udev made for F9 unfortunately do not support multiseat operation. The new GDM doesn't support multiple seats in the configuration file, ConsoleKit does not support multiple seats yet, X's --noswitchvt flag has broken, and the add-all-input-devices-to-one-X-server device model currently configued for udev and evdev is based on a single user. In contrast, F8 was the best Fedora release ever for multiseat support (though it still required a fair bit of configuration).

I want to continue to use a multiseat system, and I want to continue to use Fedora. I know that there are a lot of other people interested in doing the same, because my Multiseat howto pages (which are getting quite out of date) still receive thousands of hits each month. I also think that making Fedora multiseat-capable shines light on some corner cases (for example, using multiple video cards stresses the video drivers) and addressing bugs there will improve overall desktop reliability.

So I'd like to see really good out of the box multiseat support in Fedora 11. I've proposed it as a Fedora 11 feature and will personally be putting in as much effort as schedule allows to make this a reality.

Want to join me? You can get in touch through the comments, via e-mail (chris at tylers dot info), or on IRC (ctyler).

(Question on the side: I'm trying to collect the hardware to test multiseat across different device configurations. I think the most common video configurations will be two or more Nvidia cards (this is what I use), two or more ATI cards, and possibly on-board Intel plus one or more ATI or Nvidia cards. Does anyone know if Intel makes add-on video cards? I can't seem to find them if they do).

Multiseat Sound

nospam@example.com (Chris Tyler) — Fri, 18 Jul 2008 09:02:56 -0400

Sound on multiseat systems (computers with multiple video cards, keyboards, and mice for multiple simultaneous users) has always been a pain-point for me. The many different sound systems and interfaces made it really hard to direct sound to the right sound card.

So last summer when I upgraded my primary system -- which is a 4-user multiseat -- and lost the PCI slots I had been (trying) to use for sound, I didn't worry about it much. I bought a cheap $25 USB sound dongle and played with it a bit, but then I put sound at the bottom of my ToDo list and left it there to languish. Meanwhile the users of that system (my immediate family) got more and more frustrated with the situation.

On June 27th, Sourabh Bora left a comment on my blog asking whether DealExtreme.com's cheap USB sound dongles were good for multiseat systems. I'd never heard of DealExtreme.com before, so I checked them out, and they looked too good to be true -- a Hong Kong-based company that would sell parts for a couple of bucks and ship them anywhere in the world for free. But a bit of googling uncovered a ton of good reviews and comments, so I ordered a couple of $3.98 sound dongles to try out.

The good news is that they work well, and they're detected and configured as soon as they're plugged in because they belong to the standard USB audio class (hooray for standards!). They're not audiophile-quality, but fine for watching YouTube videos and FUDCon oggs or listening to CDs or deezer.com. And PulseAudio nicely solved the problem of redirecting sound -- I set the permission for all the sound cards so that every user could write to them, and we're using the PulseAudio "default output device" setting (via the PulseAudio volume control) to set the default sink on a per-user basis. Since our users reliably use the same seats, this works fine, though it wouldn't be a good solution where users changed seats (though that could probably be solved with a bit of PulseAudio configuration magic. Lennart and the PulseAudio team -- we really need better docs on the PulseAudio configuration file format!).

So now we have 4 users with 4 different sound outputs, a bit more peace in the family, and a new toy store for me.

It's Time for Multiseat

nospam@example.com (Chris Tyler) — Mon, 05 May 2008 23:34:42 -0400

A multiseat system is a computer set up for multiple simultaneous GUI users, using multiple graphics cards, keyboards, and mice. They're perfect for Internet cafes, library catalogs, kiosk systems, home offices, and even gaming. I've been running a 3- or 4-user multiseat system at my house for almost five years.

PulseAudio, the new GDM, recent X.org releases, ConsoleKit -- Fedora is now a better base for Multiseat than ever before, but it still requires an enormous amount of configuration to get a multiseat system running well.

If you use multiseat systems, or are interested in using them, let's get together during the FUDCon F10 hackathon and plan out a roadmap for making Fedora the best multiseat platform ever.

(Basic -- and old -- multiseat configuration information is on my blog).

TechTalk Links

nospam@example.com (Chris Tyler) — Sun, 28 Oct 2007 18:00:00 -0400

Today I had the pleasure of being interviewed by Tom D'Auria of the IMI TechTalk radio show, talking about the X Window System and my upcoming book, X Power Tools.

For the convenience of TechTalk listeners, here are some links mentioned in or related to the interview:

X.org, the community that maintains the X Window System
the Open Source Initiative and the Free Software Foundation, where you can find out about Open Source and Free Software ("Free" is this sense referring to freedom, as opposted to price -- though usually free in that sense too)
GNOME and KDE, two popular desktops based on the X Window System
the Compiz project, a very cool 3D extension to the GNOME and KDE desktops
Fedora Linux, Ubuntu, and OpenSUSE -- three Linux distributions that include the X Window System and Compiz. Download and run these from CD or install on your system to see X in action.
Seneca College Computer Studies, where I teach -- a world leader in teaching Open Source development
the Seneca Centre for Development of Open Technology
Seneca Free Software and Open Source Symposium (FSOSS 2007) - the 6th annual symposium was held last Thursday and Friday and was a great success. Videos of the symposium presentations are being posted on-line at this site.

Silent Hardware and Xen to KVM Migration

nospam@example.com (Chris Tyler) — Mon, 25 Jun 2007 21:30:29 -0400

I replaced my main home system this week. Updating that box has always been a chore because it does a lot: it's a four-user multiseat system (downtime makes the family unhappy) as well as a server (downtime makes my clients and friends unhappy). I hadn't really intended to switch to the new box yet, but there was a weird brownout on Friday (half the house had 17 volts AC, and the other half had 110) caused by a transformer failure, and replacing that transformer took longer than my UPS batteries lasted, which meant that the system had to be booted for the first time in months, which meant that a Fedora update with new X.org 'evdev' drivers kicked in, which didn't work with the old multiseat configuration file, (big breath) ... so I had to do a bunch of troubleshooting, and figured I may as well install the new box as troubleshoot a configuration that was about to be retired.

The new machine is a Core 2 Duo E6420, 4 GB, 3x500 GB SATA-2 as a 1TB RAID-5 array, 2 Asus EN7600GT Silent PCIEx16 video cards, 2 (reused) EVGA NVIDIA MX4 4000 fanless video cards, and a DVD+-RW, all in a Sonata II case.

So there's four video cards with no fans, one CPU fan, a 12 cm low-RPM case fan, a push-pull pair of power supply fans, all in an extra-rigid steel case. It's gorgeously silent compared to its predecessor. It also has enough horsepower to run AIGLX and Compiz on all four seats plus a virtual machine for the public-facing servers (including the one running this blog).

It hasn't been trivial to set up, though. Fedora 7 went on perfectly, but I need the closed-source NVIDIA driver because nv and nouveau don't work with multiseat or AIGLX (yet -- nouveau developers, I'm counting on you!) . However, the NVIDIA driver doesn't work with Xen. The paravirtualized FC6 virtual machine from the old server (32-bit FC6) wouldn't run under the new hypervisor anyways, so I knew I was in trouble. I stewed about this overnight and decided to try migrating to a fully-virtualized KVM environment in place of Xen.

This was actually fairly painless:

On the original FC6 VM, running on the old box, I installed a regular kernel in addition to the Xen kernel (yum install kernel).
I copied the VM disk image over to the new system and ran it under KVM using the virt-manager (I had to create a new, dummy VM, then swap the copied image file for the dummy one; I also had to create a bridge network configuration -- brctl addbr br0 ; ifconfig eth0 0.0.0.0 ; ifconfig br0 ipaddress).
Booted into runlevel 's' and fixed up /grub/boot/grub.conf (to select the non-Xen kernel), /etc/inittab (to disable login on the serial console and enable it on VT1), and /etc/sysconfig/network-scripts/ifcfg-eth0 (to swap the new mac address for the old one).

It took me a while to figure out those steps, but they enabled me to successfully boot the old VM on the new box.

The result: a virtually silent system with great performance, some nice eye candy, and running a stock kernel.

The Middle Mouse Button

nospam@example.com (Chris Tyler) — Mon, 07 May 2007 13:36:11 -0400

On a modern Linux system, the middle mouse button does four incredibly useful things:

It performs fast pasting. Highlight something in one window, then click the middle mouse button in another window (or another part of the same window) and the highlighted text or graphics gets pasted in. Copy'n'paste only takes a few seconds more, but I use this so often that I'm sure the seconds would add up to days.
It goes to a URL or performs a search in a web browser. Highlight a URL anywhere and then middle-click in a blank part of your Firefox (or Konqueror, or Galeon, or Epiphany) browser window and you'll go to that page. Or highlight a word or phrase without punctuation and click the middle mouse button in Firefox to perform an "I'm feeling lucky" Google search.
It opens a link in a new tab in Firefox, leaving your original page open.
It scrolls to a particular spot in your scrollbar area. If you want to scroll halfway through a document. put your cursor halfway down the scroll area and middle click -- the scrollbar will jump to where your cursor is located.

X11 conventions power some of these features, toolkits or applications power others, and some of these can be configured on other operating systems. But they're there by default on Linux, and I love the way they save me time.

No middle mouse button? Press in your scroll wheel or click the left+right buttons at the same time.

Multihead and Nvidia Drivers

nospam@example.com (Chris Tyler) — Sun, 04 Feb 2007 18:54:52 -0500

I recently updated the Nvidia drivers on my multihead Linux system and had a rude shock: the newest driver does not support my PCI-based Nvidia cards (two NV18's [GeForce4 MX 4000] and an NV17 [GeForce4 MX440]). After experimenting a bit, I realized that the Nvidia "Legacy" driver doesn't offer what I need either -- there seems to be a third driver, which is legacy-but-not-declared-legacy, the 96xx series. (On Livna, the package name for the driver is xorg-x11-drv-nvidia-96xx).

I think it's a mistake for Nvidia to stop supporting the GeForce4 video cards with the 'current' driver while those cards are still being sold. The PCI versions of the GeForce4 cards are great for multihead systems -- they have reasonable power consumption, are available in fanless versions, are inexpensive, and provide sufficient performance for basic 3D purposes (including Google Earth and even Compiz). I'm considering upgrading my 4-head home system system to a dual-core 64-bit motherboard with two PCI-Express x16 slots which will power two seats, and using two of the fanless PCI GeForce4 cards (from the existing system) for the other two seats, but I'm concerned about long-term driver support. It seems a shame to waste two perfectly good (and still available at Retail) video cards...

Multiseat X with Compiz (FC6)

nospam@example.com (Chris Tyler) — Wed, 20 Dec 2006 02:26:17 -0500

I just upgraded my 4-user multiseat system to Fedora Core 6 from FC4+X.org 6.9. The installation went fairly smoothly (though Anaconda fought with my [admittedly odd] RAID configuration and wanted to install the Grub bootloader code on /dev/md1; I switched to vt2 and used the Grub shell to set things right before rebooting).

One thing I wanted to try was AIGLX/Composite/Compiz. I thought that the OpenGL drivers for the cards might get tangled up, but that is not the case -- it actually works well, but the performance hit is heavy. It looks like a dual-core system and/or the upcoming AIGLX optimizations will be necessary to make it really usable.

It's also worth noting that X.org 7.1 seems to work better than 6.9 for multiseat operation; for example, the Zap key combination (Ctrl-Alt-Backspace) works fine on all seats. The old xorg.conf file needed only minor editing to take into account path and module changes and to add the Nvidia closed-source driver's AddARGBGLXVisuals option.