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#1 2011-04-15 14:33:14

jpsimard
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Registered: 2011-04-15
Posts: 40

Mulit-screen, Multi-card and compositing: Any hope?

In fear of the nearing death of my old system, which was of the respectable age of 6 years (and showing it), I recently splurged and bought a new system (good for another 6 years).  I now have a core i7, 12 gig ram, and 2 X gtx570.  Having two nvidia gtx570, I also bought 2 more screens and have 4 screens on the system.  I dual-boot win7 for gaming, and all my screen are easily setup with aero, but Linux is where the fun started...

Having no real choice but xinerama, meaning I had to give up compositing, which of course means no Gnome3 (fallback is no option).  Not that it mattered because Gnome2 and KDE had strange behavior with xinerama.  I get weird "slowdowns" even under XFCE, in particular with firefox.  Don't get me wrong, I'm still happy under XFCE, but I could be happier.  In particular, I don't understand the details, but xinerama must suck as nothing of the sort happens without it, driver issues or not.

And having read a whole lot of web pages, I found out that...

1) Xinerama works, but is considered deprecated and subject to problems.

2) XRandr 1.3 doesn't do multicard yet.

3) Nvidia drivers aren't what they ought to be, but then neither are those of ATI.

This rant has for a reason of existence to ask if any of you know where the hope lies.  Both "major" desktop (Gnome and KDE) use compositing in some way or other and Unity is the same.  Obviously, mulit-card, multi-screen systems aren't exactly common, but I'm getting left behind on Linux with an otherwise great system which isn't unique either!

So is it Xrandr that will solve the problem? Or will it be nouveau or even wayland?  Is stupid to hope Nvidia gets off it's rear end and solves the problem, whatever it is?  So where will the secret sauce come from?  (Information, Opinions and rants welcome)

Last edited by jpsimard (2011-04-15 14:34:06)

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#2 2011-04-15 15:57:22

BurntSushi
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From: Massachusetts
Registered: 2009-06-28
Posts: 362
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Re: Mulit-screen, Multi-card and compositing: Any hope?

At this stage in the game, if you want > 2 monitors under Linux, you need to do research before you buy the hardware :-)

As of right now, the *only* way to get compositing working on a setup with more than 2 monitors (and using a joint virtual workarea), is by using one of AMD's Eyefinity cards. (You may need to use the official Catalyst driver to get good acceleration, though, I haven't tested the open source driver with compositing yet.)

In general, you can either use something special from AMD or wait for the RandR extension to support multiple GPU's. As far as I can remember, Keith Packard said that multi-GPU support would imply a version jump to 2.0. Given that xrandr 1.4 is having problems getting out the door at the moment, I'd say you have *quite* some time before the option of running > 2 monitors with multiple GPUs (without Xinerama) becomes viable.

I suppose it's also possible that nVidia could build this into their proprietary driver, since they've completely blown off xrandr anyway. But I think that's doubtful.

In other words, you're SOL. :-(

(I recently went out and built a new computer myself. But I bought an AMD Eyefinity card, and now I have nice triple monitors :-))

Last edited by BurntSushi (2011-04-15 15:59:46)


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#3 2011-04-15 16:20:36

Awebb
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Registered: 2010-05-06
Posts: 4,176

Re: Mulit-screen, Multi-card and compositing: Any hope?

Huh? I don't get it. I have a dualscreen setup running with Xinerama, Twin view and composting. Is it really so different for four monitors on 2 nvidia cards?

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#4 2011-04-15 18:55:18

jpsimard
Member
Registered: 2011-04-15
Posts: 40

Re: Mulit-screen, Multi-card and compositing: Any hope?

Yeah, it's different...

First, TwinView is a sort of "xinerama" and it works fine with compositing.  With two cards, all hell breaks loose as for compositing.

As for the eyeinfinity, none were available at the time, and the "six screen" ones are still on backorder in my area.  Actually, there was some emergency to replace my other computer, leaving little time to wait for the "perfect part" or to actually shop around.  The old system, more or less declared an imminent death when a capacitor exploded on the motherboard, scaring the sh!t out of me.  Oddly, it kept working...  Using a system under windows was better than a dead system under Arch, as I could'nt afford to wait.  My PC is for gaming as much as work.

It's just that I see windows taking care of this with amazing ease and Xorg state of things limps around.  It would seem to me that Ubuntu and the like going hopping mad with compositing, which I don't really desire that much, seem to be forgettings that things aren't that perfect yet.

So I was wondering if somebody knew something I didn't, because if every DE is moving to compositing as a standard, maybe there was some change on the horizon I didn't know about.  There are things on the horizon with wayland and nouveau that I'll keep watching, but I know little at this time.

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#5 2011-04-15 20:09:44

BurntSushi
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From: Massachusetts
Registered: 2009-06-28
Posts: 362
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Re: Mulit-screen, Multi-card and compositing: Any hope?

Awebb wrote:

Huh? I don't get it. I have a dualscreen setup running with Xinerama, Twin view and composting. Is it really so different for four monitors on 2 nvidia cards?

You're using TwinView to setup dual monitors, not Xinerama. However, TwinView reports the screen information through the Xinerama extension. (But it's important to note that the Xinerama extension isn't the thing that is making your dual monitors work.)

jpsimard wrote:

It's just that I see windows taking care of this with amazing ease and Xorg state of things limps around.  It would seem to me that Ubuntu and the like going hopping mad with compositing, which I don't really desire that much, seem to be forgettings that things aren't that perfect yet.

So I was wondering if somebody knew something I didn't, because if every DE is moving to compositing as a standard, maybe there was some change on the horizon I didn't know about.  There are things on the horizon with wayland and nouveau that I'll keep watching, but I know little at this time.

Single and dual head setups are extremely common. Greater than 2 monitor setups are not. Compositing with the proprietary drivers tends to work quite well in the former case.

But yeah, I'm happy with the Eyefinity solution at the moment. I've been waiting years to move passed dual head.


Education is favorable to liberty. Freedom can exist only in a society of knowledge. Without learning, men are incapable of knowing their rights, and where learning is confined to a few people, liberty can be neither equal nor universal.

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#6 2011-05-02 01:14:03

ConnorBehan
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From: Long Island NY
Registered: 2007-07-05
Posts: 1,356
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Re: Mulit-screen, Multi-card and compositing: Any hope?

When you say "multi-screen, multi-card" is impossible with xrandr, do you mean "multi-monitor, multi-card"? I think it IS possible to use xrandr with multiple cards as long as each card is on a separate logical screen. This means you can't move the cursor from a monitor controlled by one card to a monitor controlled by the other - you need Ctrl+Alt+Fn to switch between them. However you can still see both screens at once and move the cursor between monitors controlled by the same card.


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#7 2011-09-30 01:25:57

mastastefant
Member
Registered: 2011-09-30
Posts: 1

Re: Mulit-screen, Multi-card and compositing: Any hope?

Hello, jpsimard,

I am truly feeling with you! I think it is now over 10 years that I am using two graphic cards in my desktop PC, starting with an secondary ISA S3 card and a primary Matrox card (if I remember correctly), more recently two PCI-e cards, and now a PCI-e Geforce GT460 and an onboard nvidia-something chip. The reason is and always has been that I wanted/needed to connect more monitors than a single card can drive. More-than-two-monitor support is only a very recent development, and only at ATI (although there have been Matrox PCI triple-head cards around, somewhen in the early paleozoikum) and has its own set of limitations. However, I will stick with nVidia cards for the desktop PC, whatever AMD does with its hardware, for a very simple reason: developer.nvidia.com versus developer.amd.com. If you want to developing GPGPU stuff, the tools and libraries of AMD cannot even begin to compete with what Nvidia provides.

In those years, I have *never* been able to get a decently working triple-head nvidia Linux setup, and I tried quite a few, like:
- Running one X server, with Twinview on one card and a single screen on the other, and connecting everything with Xinerama.
- Running one X server, one X screen for every monitor, connect everything with Xinerama.
- I even tried running two separate X.org, one for each card, forcing them on the same vt, and then connecting them by Xdmx or Synergy.

Bottom line is: If you do not use Xinerama, everything is fine and dandy, but you cannot move windows from one screen to another, since every monitor is a separate desktop. You can go as far as to enable Twinview or two screens with Xinerama on one card to get one desktop on two monitors, and a separate X to get a separate desktop on the third monitor.
As soon as you enable Xinerama over two cards, you are screwed., no matter if you run one X.org server for all cards or connect two separate X.orgs over localhost network via Xdmx. If you use a setup where you are able to move a window from one card to the other card, X.org seems to fall back to some sort of software-only rendering mode, which is both slow and buggy. Slow as in 'if you move your terminal over your KDE browser (within the same monitor!) your 2.8Ghz quad-core goes up to 80% load and you can see in which order Qt renders the elements of the webpage it displays, buggy as in: the 'File-open' dialog of opera consistently freezes X after about half an hour. At least that was the state of things when I finally gave up about a year ago and switched back to Windows-only mode on the desktop, where this stuff simply works out of the box, basically since ever (except when you want to use GPUs from different vendors, not sure if this finally truly supported). I am still monitoring every new X.org release but still waiting for the 'complete rewrite of Xinerama to fix multicard performance' changelog entry in an X.org release..

I thought about hacking Compiz back when it was still an unstable toy to somehow work around Xinerama by starting separate X.org per card without Xinerama and to let compiz handle the move-window-to-other-card stuff, but I never had the nerve to dig into it.
I even thought about trying to dig into Xinerama to find out why this stuff is so slow and somehow force it to use hardware-acceleration at least on one card, but I quickly gave up since I failed to find any documentation and the source code is not something that fills the reader with joy and inner peace..
Now I am actually beginning to fear that things are going from bad to worse since composition does not work with Xinerama setups, so the desktop will not be just slow, it wont even work at all since more and more window-managers seem to be simply requiring composition support.
I am ready to embrace any small glimpse of light and hope that Wayland will solve just everything.. if only I could believe this..
However, since Wayland will not work with the proprietary nvidia drivers as long as they do not support the features it requires (and I have little hope that they will do that before Wayland is not used widely), it is not a very interesting solution anyway, since the open-source drivers simply do not and maybe never will provide the 3D-performance that the proprietary drivers do, and I actually do want to make use of my expensive high-power high-performance GPU..

In the meantime I am hoping that Nvidia and AMD will at least get their power-consumtion fixed when more than one monitor is connected to a card (I understand that driving two monitors requires higher frequencies for the memory and GPU, but this causing the card to consume more additional power to drive the second monitor than the power consumption of the second monitor itself is ridiculus..)

This is truly one of the darker chapters of Linux.

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#8 2011-09-30 04:06:41

ConnorBehan
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From: Long Island NY
Registered: 2007-07-05
Posts: 1,356
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Re: Mulit-screen, Multi-card and compositing: Any hope?

Channel that patching energy by porting old mesa drivers to DRI2! If you still use your Matrox card, it won't have support much longer.


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#9 2011-09-30 12:27:31

Cloudef
Member
Registered: 2010-10-12
Posts: 636

Re: Mulit-screen, Multi-card and compositing: Any hope?

mastastefant, well said.
I realized this horror when I tried to help one IRC user who had problems with three monitor setup and composition, after few hours of googling and trying different things, I realized how in sad state everything was.

I am fine myself as I only have 2 monitors and use twinview, but this is only a hack.

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#10 2011-10-01 15:24:50

BurntSushi
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From: Massachusetts
Registered: 2009-06-28
Posts: 362
Website

Re: Mulit-screen, Multi-card and compositing: Any hope?

@mastastefant

The problem is a combination of nvidia's poor Linux support (by ignorning RandR >=1.2) and RandR not supporting multiple GPUs. Supposedly the latter is in the works for RandR 2.0.

You might also try your luck at the nvnews linux forum. Someone came up with a hack to tie together three monitors by using both Xinerama and TwinView. (The result is that two monitors are hardware accelerated while the third is not.)

Also, if you haven't given the open source drivers a try recently, I'd encourage you to do so. They've come a long way.


Education is favorable to liberty. Freedom can exist only in a society of knowledge. Without learning, men are incapable of knowing their rights, and where learning is confined to a few people, liberty can be neither equal nor universal.

Tu ne cede malis sed contra audentior ito

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#11 2012-04-16 05:54:29

jimduchek
Member
Registered: 2008-01-06
Posts: 8

Re: Mulit-screen, Multi-card and compositing: Any hope?

mastastefant wrote:

In the meantime I am hoping that Nvidia and AMD will at least get their power-consumtion fixed when more than one monitor is connected to a card (I understand that driving two monitors requires higher frequencies for the memory and GPU, but this causing the card to consume more additional power to drive the second monitor than the power consumption of the second monitor itself is ridiculus..)

I hate to bring up a somewhat-old thread, but as this information took me at least a day or two of messing with to figure out so I thought I'd share... At least with NVIDIA's binary drivers, this is only an issue if the two monitors attached have different modelines in their EDID.  If the two monitors have identical timings, the card will properly throttle down under normal use.  If they're even a tiny bit different (and I have two of the same model monitors that are different... wtf?), the card will run at the highest performance level.  The supposed rationale is that it prevents tearing between the two.  Don't know for sure.  I do not know if AMD cards/drivers are the same.  Most LCD's will handle timings other than what their EDID reports, so you can use the CustomEDID flag in your xorg.conf with modified EDIDs to make the two monitors match.  (Assuming of course, they're the same resolution/refresh!)

At anyrate, yeah... Multi-screen, multi-card, full acceleration really needs to happen.

Jim

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#12 2012-05-02 20:36:51

4internetanonymity
Member
Registered: 2009-07-09
Posts: 13

Re: Mulit-screen, Multi-card and compositing: Any hope?

BurntSushi wrote:

@mastastefant
The problem is a combination of nvidia's poor Linux support (by ignorning RandR >=1.2) and RandR not supporting multiple GPUs. Supposedly the latter is in the works for RandR 2.0.

So is half the puzzle solved? http://www.phoronix.com/scan.php?page=n … px=MTA5NTY

Now that the nVidia driver will support RandR 1.2/1.3, then you're saying all we need is RandR to support multiple GPUs? Now, since the problem is reduced to one piece of software (RandR), I supposed it will be easier to get together and focus on!

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#13 2012-05-03 23:00:07

BurntSushi
Member
From: Massachusetts
Registered: 2009-06-28
Posts: 362
Website

Re: Mulit-screen, Multi-card and compositing: Any hope?

4internetanonymity wrote:
BurntSushi wrote:

@mastastefant
The problem is a combination of nvidia's poor Linux support (by ignorning RandR >=1.2) and RandR not supporting multiple GPUs. Supposedly the latter is in the works for RandR 2.0.

So is half the puzzle solved? http://www.phoronix.com/scan.php?page=n … px=MTA5NTY

Now that the nVidia driver will support RandR 1.2/1.3, then you're saying all we need is RandR to support multiple GPUs? Now, since the problem is reduced to one piece of software (RandR), I supposed it will be easier to get together and focus on!

Holy shit. Indeed, half the puzzle is solved! This is outstanding news! Wow.

As far as I know, yes, multiple GPUs is only stopped by RandR. I've been keeping my eye out for news on that front, and I haven't seen anything :-( All I really know is that RandR 1.4 was supposed to be released a while ago, but something stopped it. Moreover, as far as I know, RandR 1.4 won't have any multi-GPU support.

I recall reading from Keith Packard (developer of RandR) that multi-GPU support would prompt a version jump to 2.0. It's probably a fairly substantive change. I can't find where I read this, though...


Education is favorable to liberty. Freedom can exist only in a society of knowledge. Without learning, men are incapable of knowing their rights, and where learning is confined to a few people, liberty can be neither equal nor universal.

Tu ne cede malis sed contra audentior ito

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#14 2012-05-04 15:36:33

bernarcher
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From: Germany
Registered: 2009-02-17
Posts: 2,271

Re: Mulit-screen, Multi-card and compositing: Any hope?

It appears, there is not much hope in foreseeable future. This thread has run its course...

Closing. If there is better news, please open a new one.


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